M2-M8: renderer, playback backends, GUI/network, commands, multi-version build

- M2: VideoAnchorRenderer draws width\u00d7height quad oriented by facing
- M3: VideoBackend interface + JavaCV (reflection) and WaterMedia (probe) backends
- M4: VideoConfigScreen GUI + 4 typed payloads + NBT persistence via ReadView/WriteView
- M5: stick item useOnBlock place/edit, AttackBlockCallback delete, /videoPlace /videoDelete /videoMute
- M6: per-tick distance attenuation gain = volume * clamp(1 - d/16, 0, 1), mute zeroes gain
- M7: WatermediaProbe (reflection-only; reports unavailable until v2 supports 1.21.6+)
- M8: multi-version build script (1.21.6/1.21.7/1.21.8) + Gitea Actions matrix workflow

.gitea/workflows/build.yml

@@ -0,0 +1,41 @@
+name: build-matrix
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - mc: "1.21.6"
+            yarn: "1.21.6+build.1"
+            fabric: "0.120.1+1.21.6"
+          - mc: "1.21.7"
+            yarn: "1.21.7+build.8"
+            fabric: "0.129.0+1.21.7"
+          - mc: "1.21.8"
+            yarn: "1.21.8+build.1"
+            fabric: "0.136.1+1.21.8"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+      - name: Build (MC ${{ matrix.mc }})
+        run: |
+          ./gradlew --no-daemon \
+            -Pminecraft_version=${{ matrix.mc }} \
+            -Pyarn_mappings=${{ matrix.yarn }} \
+            -Pfabric_version=${{ matrix.fabric }} \
+            build
+      - uses: actions/upload-artifact@v4
+        with:
+          name: video_player-mc${{ matrix.mc }}
+          path: build/libs/*.jar

build.gradle

@@ -26,9 +26,15 @@ dependencies {
 processResources {
     inputs.property "version", project.version
     inputs.property "mod_id", project.mod_id
+    inputs.property "minecraft_version", project.minecraft_version
+
+    // Pin the fabric.mod.json's minecraft constraint to the build's exact target — keeps each
+    // multi-version jar from claiming compatibility it doesn't have.
+    def mc = project.minecraft_version
+    def target = "~${mc}"
 
     filesMatching("fabric.mod.json") {
-        expand "version": project.version, "mod_id": project.mod_id
+        expand "version": project.version, "mod_id": project.mod_id, "target_minecraft": target
     }
 }
 

gradle.properties

@@ -3,7 +3,7 @@ org.gradle.parallel=true
 
 # Mod
 mod_id=video_player
-mod_version=0.1.0
+mod_version=0.2.0
 maven_group=com.ejclaw.videoplayer
 archives_base_name=video_player
 

scripts/build-multiver.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# Build the mod against all supported MC versions and collect jars under build/multiver/.
+# Uses gradle property overrides so we don't have to maintain three settings.gradle copies.
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+OUT=build/multiver
+rm -rf "$OUT"
+mkdir -p "$OUT"
+
+build_one() {
+  local mc="$1" yarn="$2" fab="$3"
+  echo "==> Building for MC $mc (yarn=$yarn, fabric-api=$fab)"
+  ./gradlew --no-daemon \
+    -Pminecraft_version="$mc" \
+    -Pyarn_mappings="$yarn" \
+    -Pfabric_version="$fab" \
+    build
+  # main jar = the one without "-sources"
+  local jar
+  jar=$(ls build/libs/video_player-*.jar | grep -v -- '-sources' | head -1)
+  cp "$jar" "$OUT/video_player-mc${mc}.jar"
+}
+
+build_one 1.21.6 1.21.6+build.1 0.120.1+1.21.6
+build_one 1.21.7 1.21.7+build.8 0.129.0+1.21.7
+build_one 1.21.8 1.21.8+build.1 0.136.1+1.21.8
+
+echo
+echo "All jars:"
+ls -la "$OUT"

src/main/java/com/ejclaw/videoplayer/VideoPlayerClient.java

@@ -1,15 +1,75 @@
 package com.ejclaw.videoplayer;
 
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.client.net.ClientNetworking;
+import com.ejclaw.videoplayer.client.playback.VideoPlayback;
+import com.ejclaw.videoplayer.client.render.VideoAnchorRenderer;
+import com.ejclaw.videoplayer.item.VideoStickItem;
+import com.ejclaw.videoplayer.net.DeleteAnchorPayload;
+import com.ejclaw.videoplayer.registry.VideoPlayerBlockEntities;
 import net.fabricmc.api.ClientModInitializer;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
+import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents;
+import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
+import net.fabricmc.fabric.api.client.rendering.v1.BlockEntityRendererRegistry;
+import net.fabricmc.fabric.api.event.player.AttackBlockCallback;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.network.ClientPlayerEntity;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Vec3d;
 
 @Environment(EnvType.CLIENT)
 public class VideoPlayerClient implements ClientModInitializer {
+
+    @SuppressWarnings("deprecation")
     @Override
     public void onInitializeClient() {
-        // M2+: BlockEntityRendererFactories.register(...)
+        ClientNetworking.register();
-        // M5+: AttackBlockCallback for left-click delete
+
-        VideoPlayerMod.LOG.info("[{}] client initialized (M1 scaffold)", VideoPlayerMod.MOD_ID);
+        BlockEntityRendererRegistry.register(
+            VideoPlayerBlockEntities.VIDEO_ANCHOR,
+            VideoAnchorRenderer::new
+        );
+
+        AttackBlockCallback.EVENT.register((player, world, hand, pos, direction) -> {
+            if (world.isClient
+                && player.getMainHandStack().getItem() instanceof VideoStickItem
+                && world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity) {
+                ClientPlayNetworking.send(new DeleteAnchorPayload(pos));
+                return ActionResult.SUCCESS;
+            }
+            return ActionResult.PASS;
+        });
+
+        ClientTickEvents.END_CLIENT_TICK.register(client -> {
+            VideoPlayback.tick();
+            updateDistanceGains(client);
+        });
+
+        ClientTickEvents.END_WORLD_TICK.register(world -> {
+            // no-op for now
+        });
+
+        VideoPlayerMod.LOG.info("[{}] client initialized", VideoPlayerMod.MOD_ID);
+    }
+
+    /** SPEC §6 — recompute per-anchor audio gain from player distance every tick. */
+    private static void updateDistanceGains(MinecraftClient client) {
+        ClientPlayerEntity p = client.player;
+        if (p == null || client.world == null) return;
+        Vec3d eye = p.getEyePos();
+        for (BlockPos pos : com.ejclaw.videoplayer.client.playback.VideoPlayback.activePositions()) {
+            if (!(client.world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be)) continue;
+            double dx = (pos.getX() + 0.5) - eye.x;
+            double dy = (pos.getY() + 0.5) - eye.y;
+            double dz = (pos.getZ() + 0.5) - eye.z;
+            double d  = Math.sqrt(dx * dx + dy * dy + dz * dz);
+            float attenuation = (float) Math.max(0.0, Math.min(1.0, 1.0 - d / 16.0));
+            float gain = be.isMuted() ? 0F : be.getVolume() * attenuation;
+            com.ejclaw.videoplayer.client.playback.VideoPlayback.setGain(pos, gain);
+        }
     }
 }

src/main/java/com/ejclaw/videoplayer/VideoPlayerMod.java

@@ -1,6 +1,10 @@
 package com.ejclaw.videoplayer;
 
+import com.ejclaw.videoplayer.command.VideoDeleteCommand;
+import com.ejclaw.videoplayer.command.VideoMuteCommand;
+import com.ejclaw.videoplayer.command.VideoPlaceCommand;
 import com.ejclaw.videoplayer.command.VideoStickCommand;
+import com.ejclaw.videoplayer.net.VideoPlayerNetwork;
 import com.ejclaw.videoplayer.registry.VideoPlayerBlockEntities;
 import com.ejclaw.videoplayer.registry.VideoPlayerBlocks;
 import com.ejclaw.videoplayer.registry.VideoPlayerItems;
@@ -19,10 +23,16 @@ public class VideoPlayerMod implements ModInitializer {
         VideoPlayerBlockEntities.register();
         VideoPlayerItems.register();
 
+        VideoPlayerNetwork.registerPayloadTypes();
+        VideoPlayerNetwork.registerServerReceivers();
+
         CommandRegistrationCallback.EVENT.register((dispatcher, registryAccess, env) -> {
             VideoStickCommand.register(dispatcher);
+            VideoPlaceCommand.register(dispatcher);
+            VideoDeleteCommand.register(dispatcher);
+            VideoMuteCommand.register(dispatcher);
         });
 
-        LOG.info("[{}] initialized (M1 scaffold)", MOD_ID);
+        LOG.info("[{}] initialized", MOD_ID);
     }
 }

src/main/java/com/ejclaw/videoplayer/block/VideoAnchorBlock.java

@@ -1,13 +1,22 @@
 package com.ejclaw.videoplayer.block;
 
+import com.ejclaw.videoplayer.item.VideoStickItem;
+import com.ejclaw.videoplayer.net.OpenScreenPayload;
 import com.mojang.serialization.MapCodec;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
 import net.minecraft.block.AbstractBlock;
-import net.minecraft.block.Block;
 import net.minecraft.block.BlockEntityProvider;
 import net.minecraft.block.BlockState;
 import net.minecraft.block.BlockWithEntity;
 import net.minecraft.block.entity.BlockEntity;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.ItemStack;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.Hand;
+import net.minecraft.util.hit.BlockHitResult;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
 
 public class VideoAnchorBlock extends BlockWithEntity implements BlockEntityProvider {
     public static final MapCodec<VideoAnchorBlock> CODEC = createCodec(VideoAnchorBlock::new);
@@ -25,4 +34,20 @@ public class VideoAnchorBlock extends BlockWithEntity implements BlockEntityProv
     public BlockEntity createBlockEntity(BlockPos pos, BlockState state) {
         return new VideoAnchorBlockEntity(pos, state);
     }
+
+    @Override
+    protected ActionResult onUseWithItem(ItemStack stack, BlockState state, World world,
+                                         BlockPos pos, PlayerEntity player, Hand hand,
+                                         BlockHitResult hit) {
+        if (!(stack.getItem() instanceof VideoStickItem)) {
+            return ActionResult.PASS;
+        }
+        if (world.isClient) return ActionResult.SUCCESS;
+        if (!(player instanceof ServerPlayerEntity sp)) return ActionResult.PASS;
+        if (world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be) {
+            ServerPlayNetworking.send(sp, new OpenScreenPayload(pos, be.toNbt()));
+            return ActionResult.SUCCESS;
+        }
+        return ActionResult.PASS;
+    }
 }

src/main/java/com/ejclaw/videoplayer/block/VideoAnchorBlockEntity.java

@@ -3,12 +3,15 @@ package com.ejclaw.videoplayer.block;
 import com.ejclaw.videoplayer.registry.VideoPlayerBlockEntities;
 import net.minecraft.block.BlockState;
 import net.minecraft.block.entity.BlockEntity;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.storage.ReadView;
+import net.minecraft.storage.WriteView;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Direction;
 
 /**
- * M1 placeholder. Holds the runtime fields described in SPEC §3.1; NBT persistence
+ * Anchor BE — holds the per-block config that drives playback. NBT persistence uses
- * (ReadView/WriteView in 1.21.6) lands in M3/M4 alongside the playback and GUI work.
+ * 1.21.6's ReadView/WriteView. Network sync uses {@link #toNbt()} / {@link #fromNbt(NbtCompound)}.
  */
 public class VideoAnchorBlockEntity extends BlockEntity {
     private String url = "";
@@ -33,8 +36,80 @@ public class VideoAnchorBlockEntity extends BlockEntity {
     public boolean isMuted() { return muted; }
     public boolean isAutoplay() { return autoplay; }
 
-    public void setMuted(boolean muted) {
+    public void setUrl(String url) { this.url = url == null ? "" : url; markDirty(); }
-        this.muted = muted;
+    public void setWidth(int width) { this.width = clamp(width, 1, 32); markDirty(); }
+    public void setHeight(int height) { this.height = clamp(height, 1, 32); markDirty(); }
+    public void setFacing(Direction facing) { this.facing = facing == null ? Direction.NORTH : facing; markDirty(); }
+    public void setLoop(boolean loop) { this.loop = loop; markDirty(); }
+    public void setVolume(float volume) { this.volume = Math.max(0F, Math.min(1F, volume)); markDirty(); }
+    public void setMuted(boolean muted) { this.muted = muted; markDirty(); }
+    public void setAutoplay(boolean autoplay) { this.autoplay = autoplay; markDirty(); }
+
+    /** Apply server-validated config from an NBT (used by network handler). */
+    public void applyFromNbt(NbtCompound nbt) {
+        fromNbt(nbt);
         markDirty();
     }
+
+    /** Wire-format NBT used by SaveConfig/SyncAnchor payloads. */
+    public NbtCompound toNbt() {
+        NbtCompound nbt = new NbtCompound();
+        nbt.putString("url", url);
+        nbt.putInt("width", width);
+        nbt.putInt("height", height);
+        nbt.putString("facing", facing.asString());
+        nbt.putBoolean("loop", loop);
+        nbt.putFloat("volume", volume);
+        nbt.putBoolean("muted", muted);
+        nbt.putBoolean("autoplay", autoplay);
+        return nbt;
+    }
+
+    public void fromNbt(NbtCompound nbt) {
+        this.url = clampUrl(nbt.getString("url", ""));
+        this.width = clamp(nbt.getInt("width", 1), 1, 32);
+        this.height = clamp(nbt.getInt("height", 1), 1, 32);
+        Direction d = Direction.byId(nbt.getString("facing", "north"));
+        this.facing = d == null ? Direction.NORTH : d;
+        this.loop = nbt.getBoolean("loop", true);
+        this.volume = Math.max(0F, Math.min(1F, nbt.getFloat("volume", 0.5F)));
+        this.muted = nbt.getBoolean("muted", false);
+        this.autoplay = nbt.getBoolean("autoplay", true);
+    }
+
+    @Override
+    protected void writeData(WriteView view) {
+        super.writeData(view);
+        view.putString("url", url);
+        view.putInt("width", width);
+        view.putInt("height", height);
+        view.putString("facing", facing.asString());
+        view.putBoolean("loop", loop);
+        view.putFloat("volume", volume);
+        view.putBoolean("muted", muted);
+        view.putBoolean("autoplay", autoplay);
+    }
+
+    @Override
+    protected void readData(ReadView view) {
+        super.readData(view);
+        this.url = clampUrl(view.getString("url", ""));
+        this.width = clamp(view.getInt("width", 1), 1, 32);
+        this.height = clamp(view.getInt("height", 1), 1, 32);
+        Direction d = Direction.byId(view.getString("facing", "north"));
+        this.facing = d == null ? Direction.NORTH : d;
+        this.loop = view.getBoolean("loop", true);
+        this.volume = Math.max(0F, Math.min(1F, view.getFloat("volume", 0.5F)));
+        this.muted = view.getBoolean("muted", false);
+        this.autoplay = view.getBoolean("autoplay", true);
+    }
+
+    private static int clamp(int v, int lo, int hi) {
+        return Math.max(lo, Math.min(hi, v));
+    }
+
+    private static String clampUrl(String s) {
+        if (s == null) return "";
+        return s.length() > 256 ? s.substring(0, 256) : s;
+    }
 }

src/main/java/com/ejclaw/videoplayer/client/gui/VideoConfigScreen.java

@@ -0,0 +1,154 @@
+package com.ejclaw.videoplayer.client.gui;
+
+import com.ejclaw.videoplayer.net.DeleteAnchorPayload;
+import com.ejclaw.videoplayer.net.SaveConfigPayload;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.gui.DrawContext;
+import net.minecraft.client.gui.screen.Screen;
+import net.minecraft.client.gui.widget.ButtonWidget;
+import net.minecraft.client.gui.widget.CheckboxWidget;
+import net.minecraft.client.gui.widget.SliderWidget;
+import net.minecraft.client.gui.widget.TextFieldWidget;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.text.Text;
+import net.minecraft.util.math.BlockPos;
+
+/** SPEC §4.3 — anchor config GUI. Opened by S2C {@code OpenScreenPayload}. */
+@Environment(EnvType.CLIENT)
+public class VideoConfigScreen extends Screen {
+    private final BlockPos pos;
+    private final NbtCompound initial;
+
+    private TextFieldWidget urlField;
+    private TextFieldWidget widthField;
+    private TextFieldWidget heightField;
+    private CheckboxWidget loopBox;
+    private CheckboxWidget muteBox;
+    private CheckboxWidget autoplayBox;
+    private VolumeSlider volumeSlider;
+
+    public VideoConfigScreen(BlockPos pos, NbtCompound data) {
+        super(Text.literal("Video Anchor"));
+        this.pos = pos;
+        this.initial = data;
+    }
+
+    @Override
+    protected void init() {
+        int cx = this.width / 2;
+        int y  = 40;
+
+        urlField = new TextFieldWidget(this.textRenderer, cx - 150, y, 300, 20, Text.literal("URL"));
+        urlField.setMaxLength(256);
+        urlField.setText(initial.getString("url", ""));
+        addDrawableChild(urlField);
+        y += 30;
+
+        widthField  = new TextFieldWidget(this.textRenderer, cx - 150, y, 60, 20, Text.literal("W"));
+        widthField.setMaxLength(2);
+        widthField.setText(Integer.toString(initial.getInt("width", 1)));
+        widthField.setTextPredicate(VideoConfigScreen::isDigits);
+        addDrawableChild(widthField);
+
+        heightField = new TextFieldWidget(this.textRenderer, cx - 80, y, 60, 20, Text.literal("H"));
+        heightField.setMaxLength(2);
+        heightField.setText(Integer.toString(initial.getInt("height", 1)));
+        heightField.setTextPredicate(VideoConfigScreen::isDigits);
+        addDrawableChild(heightField);
+
+        volumeSlider = new VolumeSlider(cx - 10, y, 160, 20,
+            Math.max(0F, Math.min(1F, initial.getFloat("volume", 0.5F))));
+        addDrawableChild(volumeSlider);
+        y += 30;
+
+        loopBox = CheckboxWidget.builder(Text.literal("Loop"), this.textRenderer)
+            .pos(cx - 150, y).checked(initial.getBoolean("loop", true)).build();
+        addDrawableChild(loopBox);
+
+        muteBox = CheckboxWidget.builder(Text.literal("Mute"), this.textRenderer)
+            .pos(cx - 60, y).checked(initial.getBoolean("muted", false)).build();
+        addDrawableChild(muteBox);
+
+        autoplayBox = CheckboxWidget.builder(Text.literal("Autoplay"), this.textRenderer)
+            .pos(cx + 30, y).checked(initial.getBoolean("autoplay", true)).build();
+        addDrawableChild(autoplayBox);
+        y += 36;
+
+        addDrawableChild(ButtonWidget.builder(Text.literal("Save"), b -> save())
+            .dimensions(cx - 150, y, 90, 20).build());
+        addDrawableChild(ButtonWidget.builder(Text.literal("Cancel"), b -> close())
+            .dimensions(cx - 45, y, 90, 20).build());
+        addDrawableChild(ButtonWidget.builder(Text.literal("Delete"), b -> delete())
+            .dimensions(cx + 60, y, 90, 20).build());
+    }
+
+    private void save() {
+        NbtCompound out = new NbtCompound();
+        out.putString("url", urlField.getText());
+        out.putInt("width",  parseInt(widthField.getText(), 1));
+        out.putInt("height", parseInt(heightField.getText(), 1));
+        out.putString("facing", initial.getString("facing", "north"));
+        out.putBoolean("loop", loopBox.isChecked());
+        out.putFloat("volume", volumeSlider.getVolume());
+        out.putBoolean("muted", muteBox.isChecked());
+        out.putBoolean("autoplay", autoplayBox.isChecked());
+        ClientPlayNetworking.send(new SaveConfigPayload(pos, out));
+        close();
+    }
+
+    private void delete() {
+        ClientPlayNetworking.send(new DeleteAnchorPayload(pos));
+        close();
+    }
+
+    @Override
+    public void render(DrawContext ctx, int mouseX, int mouseY, float delta) {
+        super.render(ctx, mouseX, mouseY, delta);
+        ctx.drawCenteredTextWithShadow(this.textRenderer, this.title, this.width / 2, 16, 0xFFFFFF);
+    }
+
+    @Override
+    public boolean shouldPause() { return false; }
+
+    @Override
+    public void close() {
+        MinecraftClient mc = this.client != null ? this.client : MinecraftClient.getInstance();
+        if (mc != null) mc.setScreen(null);
+    }
+
+    private static int parseInt(String s, int dflt) {
+        try { return Integer.parseInt(s); } catch (Exception e) { return dflt; }
+    }
+
+    private static boolean isDigits(String s) {
+        if (s.isEmpty()) return true;
+        for (int i = 0; i < s.length(); i++) if (!Character.isDigit(s.charAt(i))) return false;
+        return true;
+    }
+
+    private static final class VolumeSlider extends SliderWidget {
+        VolumeSlider(int x, int y, int w, int h, float initial) {
+            super(x, y, w, h, Text.literal("Volume: " + pct(initial)), initial);
+            updateMessage();
+        }
+
+        float getVolume() { return (float) this.value; }
+
+        @Override
+        protected void updateMessage() {
+            setMessage(Text.literal("Volume: " + pct((float) this.value)));
+        }
+
+        @Override
+        protected void applyValue() {
+            updateMessage();
+        }
+
+        private static int pct(float v) {
+            return Math.round(v * 100F);
+        }
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/net/ClientNetworking.java

@@ -0,0 +1,35 @@
+package com.ejclaw.videoplayer.client.net;
+
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.client.gui.VideoConfigScreen;
+import com.ejclaw.videoplayer.client.playback.VideoPlayback;
+import com.ejclaw.videoplayer.net.OpenScreenPayload;
+import com.ejclaw.videoplayer.net.SyncAnchorPayload;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
+import net.minecraft.client.MinecraftClient;
+
+/** Client-side S2C receivers for OpenScreen and SyncAnchor. */
+@Environment(EnvType.CLIENT)
+public final class ClientNetworking {
+    private ClientNetworking() {}
+
+    public static void register() {
+        ClientPlayNetworking.registerGlobalReceiver(OpenScreenPayload.ID, (payload, context) -> {
+            MinecraftClient mc = context.client();
+            mc.execute(() -> mc.setScreen(new VideoConfigScreen(payload.pos(), payload.data())));
+        });
+
+        ClientPlayNetworking.registerGlobalReceiver(SyncAnchorPayload.ID, (payload, context) -> {
+            MinecraftClient mc = context.client();
+            mc.execute(() -> {
+                if (mc.world == null) return;
+                if (mc.world.getBlockEntity(payload.pos()) instanceof VideoAnchorBlockEntity be) {
+                    be.applyFromNbt(payload.data());
+                    VideoPlayback.onConfigChanged(be);
+                }
+            });
+        });
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/playback/JavaCvBackend.java

@@ -0,0 +1,154 @@
+package com.ejclaw.videoplayer.client.playback;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+import java.lang.reflect.Method;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * SPEC §5.3 — fallback mp4/http(s) backend driven by JavaCV's FFmpegFrameGrabber.
+ *
+ * JavaCV is referenced entirely through reflection so that the mod jar stays loadable when the
+ * (large) JavaCV dependency isn't bundled — the backend just reports {@code !isReady()} until the
+ * runtime classpath contains org.bytedeco.javacv.FFmpegFrameGrabber.
+ */
+@Environment(EnvType.CLIENT)
+public class JavaCvBackend implements VideoBackend {
+    private static final String GRABBER_CLASS = "org.bytedeco.javacv.FFmpegFrameGrabber";
+    private static final String FRAME_CLASS   = "org.bytedeco.javacv.Frame";
+    private static final String CONVERTER_CLASS = "org.bytedeco.javacv.Java2DFrameConverter";
+
+    private final Object lock = new Object();
+    private Thread worker;
+    private final AtomicBoolean running = new AtomicBoolean(false);
+    private final AtomicBoolean paused  = new AtomicBoolean(false);
+    private final AtomicReference<ByteBuffer> latest = new AtomicReference<>();
+    private volatile int width = 0;
+    private volatile int height = 0;
+    private volatile float gain = 1.0F;
+    private volatile boolean loop = true;
+    private volatile boolean ready = false;
+    private volatile boolean closed = false;
+
+    @Override
+    public void play(String url, boolean loop) {
+        if (url == null || url.isEmpty()) return;
+        this.loop = loop;
+        synchronized (lock) {
+            stopWorker();
+            running.set(true);
+            paused.set(false);
+            worker = new Thread(() -> runLoop(url), "video_player-decode");
+            worker.setDaemon(true);
+            worker.start();
+        }
+    }
+
+    @Override
+    public void pause()  { paused.set(true); }
+    @Override
+    public void resume() { paused.set(false); }
+    @Override
+    public void setVolume(float g) { this.gain = Math.max(0F, Math.min(1F, g)); }
+    @Override
+    public boolean isReady() { return ready; }
+    @Override
+    public int videoWidth()  { return width; }
+    @Override
+    public int videoHeight() { return height; }
+
+    @Override
+    public ByteBuffer pollFrame() {
+        return latest.getAndSet(null);
+    }
+
+    @Override
+    public void close() {
+        closed = true;
+        stopWorker();
+    }
+
+    private void stopWorker() {
+        running.set(false);
+        Thread t = worker;
+        worker = null;
+        if (t != null) t.interrupt();
+        ready = false;
+    }
+
+    /** Pure-reflection decode loop. Silent fallback if JavaCV isn't present. */
+    private void runLoop(String url) {
+        Object grabber = null;
+        try {
+            Class<?> grabberCls = Class.forName(GRABBER_CLASS);
+            grabber = grabberCls.getConstructor(String.class).newInstance(url);
+            Method start  = grabberCls.getMethod("start");
+            Method stop   = grabberCls.getMethod("stop");
+            Method grab   = grabberCls.getMethod("grabImage");
+            Method getW   = grabberCls.getMethod("getImageWidth");
+            Method getH   = grabberCls.getMethod("getImageHeight");
+            Method setOpt = grabberCls.getMethod("setOption", String.class, String.class);
+
+            // mp4/http(s) network tuning
+            try { setOpt.invoke(grabber, "rw_timeout", "5000000"); } catch (Throwable ignored) {}
+            try { setOpt.invoke(grabber, "stimeout",   "5000000"); } catch (Throwable ignored) {}
+
+            start.invoke(grabber);
+            this.width  = (int) getW.invoke(grabber);
+            this.height = (int) getH.invoke(grabber);
+            this.ready = (width > 0 && height > 0);
+
+            Class<?> convCls = Class.forName(CONVERTER_CLASS);
+            Object converter = convCls.getDeclaredConstructor().newInstance();
+            Method toImage   = convCls.getMethod("getBufferedImage", Class.forName(FRAME_CLASS));
+
+            while (running.get() && !closed) {
+                if (paused.get()) { Thread.sleep(20); continue; }
+                Object frame = grab.invoke(grabber);
+                if (frame == null) {
+                    if (loop) {
+                        try { stop.invoke(grabber); } catch (Throwable ignored) {}
+                        try { start.invoke(grabber); } catch (Throwable ignored) {}
+                        continue;
+                    }
+                    break;
+                }
+                java.awt.image.BufferedImage img = (java.awt.image.BufferedImage) toImage.invoke(converter, frame);
+                if (img == null) continue;
+                ByteBuffer buf = toRgba(img);
+                if (buf != null) latest.set(buf);
+                Thread.sleep(15); // ~60fps cap
+            }
+        } catch (ClassNotFoundException cnf) {
+            VideoPlayerMod.LOG.info("[{}] JavaCV not on classpath; backend inactive", VideoPlayerMod.MOD_ID);
+        } catch (InterruptedException ie) {
+            Thread.currentThread().interrupt();
+        } catch (Throwable t) {
+            VideoPlayerMod.LOG.warn("[{}] JavaCV decode error: {}", VideoPlayerMod.MOD_ID, t.toString());
+        } finally {
+            ready = false;
+            if (grabber != null) {
+                try { grabber.getClass().getMethod("close").invoke(grabber); } catch (Throwable ignored) {}
+            }
+        }
+    }
+
+    private static ByteBuffer toRgba(java.awt.image.BufferedImage img) {
+        int w = img.getWidth(), h = img.getHeight();
+        int[] argb = img.getRGB(0, 0, w, h, null, 0, w);
+        ByteBuffer buf = ByteBuffer.allocateDirect(w * h * 4).order(ByteOrder.nativeOrder());
+        for (int p : argb) {
+            buf.put((byte) ((p >> 16) & 0xFF)); // R
+            buf.put((byte) ((p >>  8) & 0xFF)); // G
+            buf.put((byte) ( p        & 0xFF)); // B
+            buf.put((byte) ((p >> 24) & 0xFF)); // A
+        }
+        buf.flip();
+        return buf;
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/playback/VideoBackend.java

@@ -0,0 +1,30 @@
+package com.ejclaw.videoplayer.client.playback;
+
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+import java.nio.ByteBuffer;
+
+/**
+ * SPEC §5.3 — minimal playback backend abstraction. Implementations: WatermediaBackend (preferred,
+ * when v2 supports the target MC version) and JavaCvBackend (fallback).
+ */
+@Environment(EnvType.CLIENT)
+public interface VideoBackend {
+    void play(String url, boolean loop);
+    void pause();
+    void resume();
+    void setVolume(float gain);
+
+    boolean isReady();
+    int videoWidth();
+    int videoHeight();
+
+    /**
+     * Poll a new decoded RGBA frame if one is ready.
+     * @return the frame buffer (capacity = w*h*4) or {@code null} if no new frame is ready.
+     */
+    ByteBuffer pollFrame();
+
+    void close();
+}

src/main/java/com/ejclaw/videoplayer/client/playback/VideoPlayback.java

@@ -0,0 +1,149 @@
+package com.ejclaw.videoplayer.client.playback;
+
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.texture.NativeImage;
+import net.minecraft.client.texture.NativeImageBackedTexture;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+/**
+ * SPEC §5 — per-anchor playback registry. Maps {@link BlockPos} → ({@link VideoBackend} + dynamic
+ * Identifier of an {@link NativeImageBackedTexture}). The renderer reads the texture id and binds
+ * it to the quad; this class drives the frame pump every client tick.
+ */
+@Environment(EnvType.CLIENT)
+public final class VideoPlayback {
+    private VideoPlayback() {}
+
+    private static final Map<BlockPos, Entry> ENTRIES = new HashMap<>();
+
+    public static Identifier getOrStart(VideoAnchorBlockEntity be) {
+        BlockPos pos = be.getPos();
+        Entry e = ENTRIES.get(pos);
+        if (e != null && e.url.equals(be.getUrl())) {
+            return e.id;
+        }
+        if (e != null) {
+            stop(pos);
+        }
+        if (be.getUrl().isEmpty() || !be.isAutoplay()) {
+            return null;
+        }
+        VideoBackend backend = WatermediaProbe.isAvailable() ? new WatermediaBackend() : new JavaCvBackend();
+        backend.play(be.getUrl(), be.isLoop());
+        backend.setVolume(be.isMuted() ? 0F : be.getVolume());
+        Entry created = new Entry(be.getUrl(), backend);
+        ENTRIES.put(pos, created);
+        return created.id;
+    }
+
+    public static Identifier currentTexture(BlockPos pos) {
+        Entry e = ENTRIES.get(pos);
+        return e == null ? null : e.id;
+    }
+
+    public static void stop(BlockPos pos) {
+        Entry e = ENTRIES.remove(pos);
+        if (e != null) e.close();
+    }
+
+    public static void onConfigChanged(VideoAnchorBlockEntity be) {
+        Entry e = ENTRIES.get(be.getPos());
+        if (e == null) return;
+        if (!e.url.equals(be.getUrl())) {
+            stop(be.getPos());
+            return;
+        }
+        e.backend.setVolume(be.isMuted() ? 0F : be.getVolume());
+    }
+
+    /** Called every client tick to upload new frames into the GPU texture. */
+    public static void tick() {
+        if (MinecraftClient.getInstance() == null) return;
+        Iterator<Map.Entry<BlockPos, Entry>> it = ENTRIES.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<BlockPos, Entry> me = it.next();
+            Entry e = me.getValue();
+            if (!e.backend.isReady()) continue;
+            ByteBuffer buf = e.backend.pollFrame();
+            if (buf == null) continue;
+            try {
+                e.upload(buf);
+            } catch (Throwable t) {
+                // texture upload errors shouldn't kill the client; drop this entry
+                e.close();
+                it.remove();
+            }
+        }
+    }
+
+    public static java.util.Set<BlockPos> activePositions() {
+        return new java.util.HashSet<>(ENTRIES.keySet());
+    }
+
+    public static void setGain(BlockPos pos, float gain) {
+        Entry e = ENTRIES.get(pos);
+        if (e != null) e.backend.setVolume(gain);
+    }
+
+    public static void stopAll() {
+        for (Entry e : ENTRIES.values()) e.close();
+        ENTRIES.clear();
+    }
+
+    private static final class Entry {
+        final String url;
+        final VideoBackend backend;
+        final Identifier id;
+        NativeImageBackedTexture texture;
+        int texW = 0, texH = 0;
+
+        Entry(String url, VideoBackend backend) {
+            this.url = url;
+            this.backend = backend;
+            this.id = Identifier.of("video_player", "dynamic/" + Integer.toHexString(System.identityHashCode(this)));
+        }
+
+        void upload(ByteBuffer rgba) {
+            int w = backend.videoWidth();
+            int h = backend.videoHeight();
+            if (w <= 0 || h <= 0) return;
+            if (texture == null || w != texW || h != texH) {
+                if (texture != null) texture.close();
+                NativeImage img = new NativeImage(NativeImage.Format.RGBA, w, h, false);
+                texture = new NativeImageBackedTexture(() -> "video_player_dyn", img);
+                MinecraftClient.getInstance().getTextureManager().registerTexture(id, texture);
+                texW = w; texH = h;
+            }
+            NativeImage img = texture.getImage();
+            if (img == null) return;
+            // copy buf → image pixels (RGBA bytes, native order)
+            int pixels = w * h;
+            for (int i = 0; i < pixels; i++) {
+                int r = rgba.get() & 0xFF;
+                int g = rgba.get() & 0xFF;
+                int b = rgba.get() & 0xFF;
+                int a = rgba.get() & 0xFF;
+                int argb = (a << 24) | (r << 16) | (g << 8) | b;
+                img.setColorArgb(i % w, i / w, argb);
+            }
+            texture.upload();
+        }
+
+        void close() {
+            backend.close();
+            if (texture != null) {
+                texture.close();
+                texture = null;
+            }
+        }
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/playback/WatermediaBackend.java

@@ -0,0 +1,50 @@
+package com.ejclaw.videoplayer.client.playback;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+import java.nio.ByteBuffer;
+
+/**
+ * SPEC §5.3 / §5.4 — WaterMedia v2 backend. Reflection-only so the mod jar stays clean of
+ * compile-time WaterMedia dependencies. Until a v2 build supports 1.21.6+ this returns
+ * {@code !isReady()} and {@link WatermediaProbe} reports unavailable, so callers fall through
+ * to {@link JavaCvBackend}.
+ */
+@Environment(EnvType.CLIENT)
+public class WatermediaBackend implements VideoBackend {
+    private volatile boolean ready = false;
+    private volatile int width = 0;
+    private volatile int height = 0;
+    private volatile float gain = 1.0F;
+    private Object player;
+
+    @Override
+    public void play(String url, boolean loop) {
+        if (!WatermediaProbe.isAvailable()) {
+            VideoPlayerMod.LOG.debug("[{}] WatermediaBackend.play called but probe says unavailable",
+                VideoPlayerMod.MOD_ID);
+            return;
+        }
+        // Reflection construction skipped — only reachable when WaterMedia v2 ships for the target MC.
+    }
+
+    @Override public void pause() {}
+    @Override public void resume() {}
+    @Override public void setVolume(float g) { this.gain = Math.max(0F, Math.min(1F, g)); }
+    @Override public boolean isReady() { return ready; }
+    @Override public int videoWidth()  { return width; }
+    @Override public int videoHeight() { return height; }
+
+    @Override
+    public ByteBuffer pollFrame() {
+        return null; // no frames until v2 is wired up
+    }
+
+    @Override
+    public void close() {
+        ready = false;
+        player = null;
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/playback/WatermediaProbe.java

@@ -0,0 +1,35 @@
+package com.ejclaw.videoplayer.client.playback;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+/**
+ * SPEC §5.4 — Reflection-only check for whether WaterMedia v2 is present and usable on this MC.
+ * As of 1.21.6+ WaterMedia v2 has no Yarn-mapped artifact, so this always reports false; we keep the
+ * shape so the mod will auto-prefer WaterMedia when a future build adds it.
+ */
+@Environment(EnvType.CLIENT)
+public final class WatermediaProbe {
+    private WatermediaProbe() {}
+
+    private static final Boolean CACHED = compute();
+
+    public static boolean isAvailable() {
+        return CACHED;
+    }
+
+    private static boolean compute() {
+        try {
+            Class.forName("me.srrapero720.watermedia.api.WaterMediaAPI", false,
+                WatermediaProbe.class.getClassLoader());
+            VideoPlayerMod.LOG.info("[{}] WaterMedia v2 detected", VideoPlayerMod.MOD_ID);
+            return true;
+        } catch (ClassNotFoundException e) {
+            return false;
+        } catch (Throwable t) {
+            VideoPlayerMod.LOG.warn("[{}] WaterMedia probe failed: {}", VideoPlayerMod.MOD_ID, t.toString());
+            return false;
+        }
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/render/VideoAnchorRenderer.java

@@ -0,0 +1,91 @@
+package com.ejclaw.videoplayer.client.render;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.client.playback.VideoPlayback;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+import net.minecraft.client.render.RenderLayer;
+import net.minecraft.client.render.VertexConsumer;
+import net.minecraft.client.render.VertexConsumerProvider;
+import net.minecraft.client.render.block.entity.BlockEntityRenderer;
+import net.minecraft.client.render.block.entity.BlockEntityRendererFactory;
+import net.minecraft.client.util.math.MatrixStack;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.Direction;
+import net.minecraft.util.math.RotationAxis;
+import net.minecraft.util.math.Vec3d;
+import org.joml.Matrix4f;
+
+/** SPEC §5.2 — draws a width × height quad in front of the anchor, oriented by facing. */
+@Environment(EnvType.CLIENT)
+public class VideoAnchorRenderer implements BlockEntityRenderer<VideoAnchorBlockEntity> {
+
+    /** Placeholder texture used until a frame is uploaded. */
+    private static final Identifier PLACEHOLDER =
+        Identifier.of(VideoPlayerMod.MOD_ID, "block/video_anchor");
+
+    public VideoAnchorRenderer(BlockEntityRendererFactory.Context ctx) {
+        // no-op — context kept for future symbol/lookup needs
+    }
+
+    @Override
+    public void render(VideoAnchorBlockEntity be, float tickDelta, MatrixStack matrices,
+                       VertexConsumerProvider vertices, int light, int overlay, Vec3d cam) {
+        Identifier tex = VideoPlayback.currentTexture(be.getPos());
+        Identifier bound = tex != null ? tex : PLACEHOLDER;
+
+        float w = be.getWidth();
+        float h = be.getHeight();
+        Direction facing = be.getFacing();
+
+        matrices.push();
+        // Center the quad above the anchor's top face, then rotate to facing.
+        matrices.translate(0.5, 1.01, 0.5);
+        float rot = facing.getAxis().isHorizontal()
+            ? Direction.getHorizontalDegreesOrThrow(facing)
+            : 0F;
+        matrices.multiply(RotationAxis.POSITIVE_Y.rotationDegrees(-rot));
+        matrices.translate(-w / 2.0F, 0, 0);
+
+        VertexConsumer vc = vertices.getBuffer(RenderLayer.getEntityCutoutNoCull(bound));
+        Matrix4f mat = matrices.peek().getPositionMatrix();
+
+        // Two-sided quad in the XY plane at z=0
+        emit(vc, mat, 0, 0, 0, 0, 1, light, overlay);
+        emit(vc, mat, w, 0, 0, 1, 1, light, overlay);
+        emit(vc, mat, w, h, 0, 1, 0, light, overlay);
+        emit(vc, mat, 0, h, 0, 0, 0, light, overlay);
+        // back face (so the anchor is visible from behind too)
+        emit(vc, mat, 0, h, 0, 0, 0, light, overlay);
+        emit(vc, mat, w, h, 0, 1, 0, light, overlay);
+        emit(vc, mat, w, 0, 0, 1, 1, light, overlay);
+        emit(vc, mat, 0, 0, 0, 0, 1, light, overlay);
+
+        matrices.pop();
+
+        // Trigger playback startup lazily, on first frame the camera sees the BE.
+        VideoPlayback.getOrStart(be);
+    }
+
+    private static void emit(VertexConsumer vc, Matrix4f mat,
+                             float x, float y, float z, float u, float v,
+                             int light, int overlay) {
+        vc.vertex(mat, x, y, z)
+          .color(255, 255, 255, 255)
+          .texture(u, v)
+          .overlay(overlay)
+          .light(light)
+          .normal(0F, 0F, 1F);
+    }
+
+    @Override
+    public boolean rendersOutsideBoundingBox() {
+        return true;
+    }
+
+    @Override
+    public int getRenderDistance() {
+        return 128;
+    }
+}

src/main/java/com/ejclaw/videoplayer/command/VideoDeleteCommand.java

@@ -0,0 +1,44 @@
+package com.ejclaw.videoplayer.command;
+
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import net.minecraft.block.Blocks;
+import net.minecraft.command.argument.BlockPosArgumentType;
+import net.minecraft.server.command.CommandManager;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.text.Text;
+import net.minecraft.util.math.BlockPos;
+
+/** SPEC §4.5.1 — {@code /videoDelete <pos>} */
+public final class VideoDeleteCommand {
+    private VideoDeleteCommand() {}
+
+    public static void register(CommandDispatcher<ServerCommandSource> dispatcher) {
+        dispatcher.register(register("videoDelete"));
+        dispatcher.register(register("videodelete"));
+    }
+
+    private static com.mojang.brigadier.builder.LiteralArgumentBuilder<ServerCommandSource>
+    register(String name) {
+        return CommandManager.literal(name)
+            .requires(s -> s.hasPermissionLevel(2))
+            .then(CommandManager.argument("pos", BlockPosArgumentType.blockPos())
+                .executes(VideoDeleteCommand::run));
+    }
+
+    private static int run(com.mojang.brigadier.context.CommandContext<ServerCommandSource> ctx)
+            throws CommandSyntaxException {
+        ServerCommandSource src = ctx.getSource();
+        ServerWorld world = src.getWorld();
+        BlockPos pos = BlockPosArgumentType.getLoadedBlockPos(ctx, "pos");
+        if (!(world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity)) {
+            src.sendError(Text.literal("no anchor at that position"));
+            return 0;
+        }
+        world.setBlockState(pos, Blocks.AIR.getDefaultState());
+        src.sendFeedback(() -> Text.literal("anchor deleted at " + pos.toShortString()), true);
+        return 1;
+    }
+}

src/main/java/com/ejclaw/videoplayer/command/VideoMuteCommand.java

@@ -0,0 +1,61 @@
+package com.ejclaw.videoplayer.command;
+
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.net.SyncAnchorPayload;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import net.fabricmc.fabric.api.networking.v1.PlayerLookup;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.command.argument.BlockPosArgumentType;
+import net.minecraft.server.command.CommandManager;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.text.Text;
+import net.minecraft.util.math.BlockPos;
+
+/** SPEC §4.5.1 — {@code /videoMute <pos> <on|off>} */
+public final class VideoMuteCommand {
+    private VideoMuteCommand() {}
+
+    public static void register(CommandDispatcher<ServerCommandSource> dispatcher) {
+        dispatcher.register(register("videoMute"));
+        dispatcher.register(register("videomute"));
+    }
+
+    private static com.mojang.brigadier.builder.LiteralArgumentBuilder<ServerCommandSource>
+    register(String name) {
+        return CommandManager.literal(name)
+            .requires(s -> s.hasPermissionLevel(2))
+            .then(CommandManager.argument("pos", BlockPosArgumentType.blockPos())
+                .then(CommandManager.argument("state", StringArgumentType.word())
+                    .executes(VideoMuteCommand::run)));
+    }
+
+    private static int run(com.mojang.brigadier.context.CommandContext<ServerCommandSource> ctx)
+            throws CommandSyntaxException {
+        ServerCommandSource src = ctx.getSource();
+        ServerWorld world = src.getWorld();
+        BlockPos pos = BlockPosArgumentType.getLoadedBlockPos(ctx, "pos");
+        String state = StringArgumentType.getString(ctx, "state").toLowerCase();
+        boolean muted;
+        if ("on".equals(state) || "true".equals(state))      muted = true;
+        else if ("off".equals(state) || "false".equals(state)) muted = false;
+        else {
+            src.sendError(Text.literal("state must be on/off"));
+            return 0;
+        }
+        if (!(world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be)) {
+            src.sendError(Text.literal("no anchor at that position"));
+            return 0;
+        }
+        be.setMuted(muted);
+        for (ServerPlayerEntity p : PlayerLookup.tracking(world, pos)) {
+            ServerPlayNetworking.send(p, new SyncAnchorPayload(pos, be.toNbt()));
+        }
+        final boolean mFinal = muted;
+        src.sendFeedback(() -> Text.literal("anchor " + (mFinal ? "muted" : "unmuted")), true);
+        return 1;
+    }
+}

src/main/java/com/ejclaw/videoplayer/command/VideoPlaceCommand.java

@@ -0,0 +1,81 @@
+package com.ejclaw.videoplayer.command;
+
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.net.SyncAnchorPayload;
+import com.ejclaw.videoplayer.registry.VideoPlayerBlocks;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.arguments.FloatArgumentType;
+import com.mojang.brigadier.arguments.IntegerArgumentType;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import net.fabricmc.fabric.api.networking.v1.PlayerLookup;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.command.argument.BlockPosArgumentType;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.server.command.CommandManager;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.text.Text;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Direction;
+
+/** SPEC §4.5.1 — {@code /videoPlace <pos> <facing> <width> <height> <url>} */
+public final class VideoPlaceCommand {
+    private VideoPlaceCommand() {}
+
+    public static void register(CommandDispatcher<ServerCommandSource> dispatcher) {
+        dispatcher.register(register("videoPlace"));
+        dispatcher.register(register("videoplace"));
+    }
+
+    private static com.mojang.brigadier.builder.LiteralArgumentBuilder<ServerCommandSource>
+    register(String name) {
+        return CommandManager.literal(name)
+            .requires(s -> s.hasPermissionLevel(2))
+            .then(CommandManager.argument("pos", BlockPosArgumentType.blockPos())
+                .then(CommandManager.argument("facing", StringArgumentType.word())
+                    .then(CommandManager.argument("width", IntegerArgumentType.integer(1, 32))
+                        .then(CommandManager.argument("height", IntegerArgumentType.integer(1, 32))
+                            .then(CommandManager.argument("url", StringArgumentType.greedyString())
+                                .executes(VideoPlaceCommand::run))))));
+    }
+
+    private static int run(com.mojang.brigadier.context.CommandContext<ServerCommandSource> ctx)
+            throws CommandSyntaxException {
+        ServerCommandSource src = ctx.getSource();
+        ServerWorld world = src.getWorld();
+        BlockPos pos = BlockPosArgumentType.getLoadedBlockPos(ctx, "pos");
+        Direction facing = Direction.byId(StringArgumentType.getString(ctx, "facing"));
+        if (facing == null) {
+            src.sendError(Text.literal("facing must be north/south/east/west/up/down"));
+            return 0;
+        }
+        int width  = IntegerArgumentType.getInteger(ctx, "width");
+        int height = IntegerArgumentType.getInteger(ctx, "height");
+        String url = StringArgumentType.getString(ctx, "url").trim();
+        if (!url.isEmpty() && !(url.startsWith("http://") || url.startsWith("https://"))) {
+            src.sendError(Text.literal("url must be http:// or https:// (or empty)"));
+            return 0;
+        }
+        if (url.length() > 256) url = url.substring(0, 256);
+
+        world.setBlockState(pos, VideoPlayerBlocks.VIDEO_ANCHOR.getDefaultState());
+        if (!(world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be)) {
+            src.sendError(Text.literal("failed to place anchor"));
+            return 0;
+        }
+        be.setFacing(facing);
+        be.setWidth(width);
+        be.setHeight(height);
+        be.setUrl(url);
+
+        NbtCompound nbt = be.toNbt();
+        for (ServerPlayerEntity p : PlayerLookup.tracking(world, pos)) {
+            ServerPlayNetworking.send(p, new SyncAnchorPayload(pos, nbt));
+        }
+        final BlockPos fp = pos;
+        src.sendFeedback(() -> Text.literal("anchor placed at " + fp.toShortString()), true);
+        return 1;
+    }
+}

src/main/java/com/ejclaw/videoplayer/item/VideoStickItem.java

@@ -1,12 +1,60 @@
 package com.ejclaw.videoplayer.item;
 
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.net.OpenScreenPayload;
+import com.ejclaw.videoplayer.registry.VideoPlayerBlocks;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.block.Block;
+import net.minecraft.block.BlockState;
+import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.Item;
+import net.minecraft.item.ItemUsageContext;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.ActionResult;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Direction;
+import net.minecraft.world.World;
 
-/**
+/** SPEC §4.2 — right-click empty face → place anchor + open GUI. Right-click existing anchor → edit. */
- * M1: registered placeholder. Right/left-click handlers land in M4–M5.
- */
 public class VideoStickItem extends Item {
     public VideoStickItem(Settings settings) {
         super(settings);
     }
+
+    @Override
+    public ActionResult useOnBlock(ItemUsageContext ctx) {
+        World world = ctx.getWorld();
+        if (world.isClient) {
+            // server is authoritative; client just consumes the gesture
+            return ActionResult.SUCCESS;
+        }
+
+        ServerWorld sw = (ServerWorld) world;
+        PlayerEntity player = ctx.getPlayer();
+        if (!(player instanceof ServerPlayerEntity sp)) return ActionResult.PASS;
+
+        BlockPos hit = ctx.getBlockPos();
+
+        // Existing anchor → edit
+        if (sw.getBlockEntity(hit) instanceof VideoAnchorBlockEntity existing) {
+            ServerPlayNetworking.send(sp, new OpenScreenPayload(hit, existing.toNbt()));
+            return ActionResult.SUCCESS;
+        }
+
+        // Empty face → place anchor on top of the clicked face
+        Direction side = ctx.getSide();
+        BlockPos placeAt = hit.offset(side);
+        BlockState there = sw.getBlockState(placeAt);
+        if (!there.isReplaceable()) return ActionResult.PASS;
+
+        Block anchor = VideoPlayerBlocks.VIDEO_ANCHOR;
+        sw.setBlockState(placeAt, anchor.getDefaultState());
+
+        if (sw.getBlockEntity(placeAt) instanceof VideoAnchorBlockEntity be) {
+            be.setFacing(ctx.getHorizontalPlayerFacing().getOpposite());
+            ServerPlayNetworking.send(sp, new OpenScreenPayload(placeAt, be.toNbt()));
+        }
+        return ActionResult.SUCCESS;
+    }
 }

src/main/java/com/ejclaw/videoplayer/net/DeleteAnchorPayload.java

@@ -0,0 +1,24 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.network.RegistryByteBuf;
+import net.minecraft.network.codec.PacketCodec;
+import net.minecraft.network.packet.CustomPayload;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+
+/** C2S — delete an anchor from the VideoConfigScreen. */
+public record DeleteAnchorPayload(BlockPos pos) implements CustomPayload {
+    public static final CustomPayload.Id<DeleteAnchorPayload> ID =
+        new CustomPayload.Id<>(Identifier.of(VideoPlayerMod.MOD_ID, "delete_anchor"));
+
+    public static final PacketCodec<RegistryByteBuf, DeleteAnchorPayload> CODEC = PacketCodec.tuple(
+        BlockPos.PACKET_CODEC, DeleteAnchorPayload::pos,
+        DeleteAnchorPayload::new
+    );
+
+    @Override
+    public Id<? extends CustomPayload> getId() {
+        return ID;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/OpenScreenPayload.java

@@ -0,0 +1,27 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.network.RegistryByteBuf;
+import net.minecraft.network.codec.PacketCodec;
+import net.minecraft.network.codec.PacketCodecs;
+import net.minecraft.network.packet.CustomPayload;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+
+/** S2C — open the VideoConfigScreen for an anchor on the client. */
+public record OpenScreenPayload(BlockPos pos, NbtCompound data) implements CustomPayload {
+    public static final CustomPayload.Id<OpenScreenPayload> ID =
+        new CustomPayload.Id<>(Identifier.of(VideoPlayerMod.MOD_ID, "open_screen"));
+
+    public static final PacketCodec<RegistryByteBuf, OpenScreenPayload> CODEC = PacketCodec.tuple(
+        BlockPos.PACKET_CODEC, OpenScreenPayload::pos,
+        PacketCodecs.NBT_COMPOUND, OpenScreenPayload::data,
+        OpenScreenPayload::new
+    );
+
+    @Override
+    public Id<? extends CustomPayload> getId() {
+        return ID;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/SaveConfigPayload.java

@@ -0,0 +1,27 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.network.RegistryByteBuf;
+import net.minecraft.network.codec.PacketCodec;
+import net.minecraft.network.codec.PacketCodecs;
+import net.minecraft.network.packet.CustomPayload;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+
+/** C2S — save edited config from VideoConfigScreen back to the server. */
+public record SaveConfigPayload(BlockPos pos, NbtCompound data) implements CustomPayload {
+    public static final CustomPayload.Id<SaveConfigPayload> ID =
+        new CustomPayload.Id<>(Identifier.of(VideoPlayerMod.MOD_ID, "save_config"));
+
+    public static final PacketCodec<RegistryByteBuf, SaveConfigPayload> CODEC = PacketCodec.tuple(
+        BlockPos.PACKET_CODEC, SaveConfigPayload::pos,
+        PacketCodecs.NBT_COMPOUND, SaveConfigPayload::data,
+        SaveConfigPayload::new
+    );
+
+    @Override
+    public Id<? extends CustomPayload> getId() {
+        return ID;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/SyncAnchorPayload.java

@@ -0,0 +1,27 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.network.RegistryByteBuf;
+import net.minecraft.network.codec.PacketCodec;
+import net.minecraft.network.codec.PacketCodecs;
+import net.minecraft.network.packet.CustomPayload;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+
+/** S2C — push current anchor state (URL/dims/loop/volume/muted/autoplay) to clients in range. */
+public record SyncAnchorPayload(BlockPos pos, NbtCompound data) implements CustomPayload {
+    public static final CustomPayload.Id<SyncAnchorPayload> ID =
+        new CustomPayload.Id<>(Identifier.of(VideoPlayerMod.MOD_ID, "sync_anchor"));
+
+    public static final PacketCodec<RegistryByteBuf, SyncAnchorPayload> CODEC = PacketCodec.tuple(
+        BlockPos.PACKET_CODEC, SyncAnchorPayload::pos,
+        PacketCodecs.NBT_COMPOUND, SyncAnchorPayload::data,
+        SyncAnchorPayload::new
+    );
+
+    @Override
+    public Id<? extends CustomPayload> getId() {
+        return ID;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/VideoPlayerNetwork.java

@@ -0,0 +1,106 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import net.fabricmc.fabric.api.networking.v1.PayloadTypeRegistry;
+import net.fabricmc.fabric.api.networking.v1.PlayerLookup;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.block.Blocks;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.math.BlockPos;
+
+/**
+ * Registers all four payload types and the two C2S server-side receivers.
+ * Client-side receivers are registered in {@code com.ejclaw.videoplayer.client.net.ClientNetworking}.
+ */
+public final class VideoPlayerNetwork {
+    private VideoPlayerNetwork() {}
+
+    public static void registerPayloadTypes() {
+        // S2C
+        PayloadTypeRegistry.playS2C().register(OpenScreenPayload.ID, OpenScreenPayload.CODEC);
+        PayloadTypeRegistry.playS2C().register(SyncAnchorPayload.ID, SyncAnchorPayload.CODEC);
+        // C2S
+        PayloadTypeRegistry.playC2S().register(SaveConfigPayload.ID, SaveConfigPayload.CODEC);
+        PayloadTypeRegistry.playC2S().register(DeleteAnchorPayload.ID, DeleteAnchorPayload.CODEC);
+    }
+
+    public static void registerServerReceivers() {
+        ServerPlayNetworking.registerGlobalReceiver(SaveConfigPayload.ID, (payload, context) -> {
+            ServerPlayerEntity player = context.player();
+            ServerWorld world = player.getWorld();
+            BlockPos pos = payload.pos();
+            context.server().execute(() -> handleSave(world, player, pos, payload.data()));
+        });
+
+        ServerPlayNetworking.registerGlobalReceiver(DeleteAnchorPayload.ID, (payload, context) -> {
+            ServerPlayerEntity player = context.player();
+            ServerWorld world = player.getWorld();
+            BlockPos pos = payload.pos();
+            context.server().execute(() -> handleDelete(world, player, pos));
+        });
+    }
+
+    private static void handleSave(ServerWorld world, ServerPlayerEntity player, BlockPos pos, NbtCompound data) {
+        if (!canModify(player, pos)) {
+            VideoPlayerMod.LOG.warn("[{}] {} attempted save without permission at {}",
+                VideoPlayerMod.MOD_ID, player.getName().getString(), pos);
+            return;
+        }
+        if (!(world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be)) {
+            return;
+        }
+        be.applyFromNbt(sanitize(data));
+        // broadcast updated state to all players tracking the chunk
+        SyncAnchorPayload sync = new SyncAnchorPayload(pos, be.toNbt());
+        for (ServerPlayerEntity watcher : PlayerLookup.tracking(world, pos)) {
+            ServerPlayNetworking.send(watcher, sync);
+        }
+    }
+
+    private static void handleDelete(ServerWorld world, ServerPlayerEntity player, BlockPos pos) {
+        if (!canModify(player, pos)) {
+            return;
+        }
+        if (world.getBlockEntity(pos) instanceof VideoAnchorBlockEntity) {
+            world.setBlockState(pos, Blocks.AIR.getDefaultState());
+        }
+    }
+
+    /** Permission check: creative players or operators may modify anchors. */
+    public static boolean canModify(ServerPlayerEntity player, BlockPos pos) {
+        if (player.isCreative()) return true;
+        return player.hasPermissionLevel(2);
+    }
+
+    /** Strip out unexpected keys from C2S NBT before applying. */
+    private static NbtCompound sanitize(NbtCompound in) {
+        NbtCompound out = new NbtCompound();
+        out.putString("url", trimUrl(in.getString("url", "")));
+        out.putInt("width", clamp(in.getInt("width", 1), 1, 32));
+        out.putInt("height", clamp(in.getInt("height", 1), 1, 32));
+        out.putString("facing", in.getString("facing", "north"));
+        out.putBoolean("loop", in.getBoolean("loop", true));
+        out.putFloat("volume", Math.max(0F, Math.min(1F, in.getFloat("volume", 0.5F))));
+        out.putBoolean("muted", in.getBoolean("muted", false));
+        out.putBoolean("autoplay", in.getBoolean("autoplay", true));
+        return out;
+    }
+
+    private static String trimUrl(String s) {
+        if (s == null) return "";
+        String t = s.trim();
+        if (t.length() > 256) t = t.substring(0, 256);
+        // SPEC §4.4: only https?:// or empty
+        if (!t.isEmpty() && !(t.startsWith("http://") || t.startsWith("https://"))) {
+            return "";
+        }
+        return t;
+    }
+
+    private static int clamp(int v, int lo, int hi) {
+        return Math.max(lo, Math.min(hi, v));
+    }
+}

src/main/resources/assets/video_player/blockstates/video_anchor.json

@@ -0,0 +1,5 @@
+{
+  "variants": {
+    "": { "model": "video_player:block/video_anchor" }
+  }
+}

src/main/resources/assets/video_player/models/block/video_anchor.json

@@ -0,0 +1,21 @@
+{
+  "parent": "block/block",
+  "textures": {
+    "all": "video_player:block/video_anchor",
+    "particle": "video_player:block/video_anchor"
+  },
+  "elements": [
+    {
+      "from": [0, 0, 0],
+      "to": [16, 2, 16],
+      "faces": {
+        "down":  { "texture": "#all", "uv": [0, 0, 16, 16] },
+        "up":    { "texture": "#all", "uv": [0, 0, 16, 16] },
+        "north": { "texture": "#all", "uv": [0, 0, 16, 2] },
+        "south": { "texture": "#all", "uv": [0, 0, 16, 2] },
+        "east":  { "texture": "#all", "uv": [0, 0, 16, 2] },
+        "west":  { "texture": "#all", "uv": [0, 0, 16, 2] }
+      }
+    }
+  ]
+}

src/main/resources/assets/video_player/models/item/video_stick.json

@@ -0,0 +1,6 @@
+{
+  "parent": "item/generated",
+  "textures": {
+    "layer0": "video_player:item/video_stick"
+  }
+}

src/main/resources/fabric.mod.json

@@ -18,7 +18,7 @@
   "depends": {
     "fabricloader": ">=0.16.0",
     "fabric-api": "*",
-    "minecraft": ">=1.21.6",
+    "minecraft": "${target_minecraft}",
     "java": ">=21"
   }
 }