diff --git a/README.md b/README.md
index 5cea3bc..de9bb21 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,8 @@ TETR.IO 스타일의 **모바일 실시간 대전 블록 스태커** 웹 게임.
 
 이 문서는 앱 제작을 위한 **최종 빌드 진입점(entry point)** 이다. 모든 설계 결정·수치·에셋의 **정본(source of truth)은 [`TETRIG-최종명세서.md`](./TETRIG-최종명세서.md)** 이며, 구현 시 반드시 명세서와 UX 목업을 함께 열어 작업한다.
 
+> **클라이언트 변경 (2026-08-22 사용자 결정)**: 플레이스토어 출시를 위해 클라이언트를 **네이티브 Android (Kotlin + Jetpack Compose)** 로 제작한다. 소스는 [`android/`](./android). 코어 게임 로직은 UI와 분리된 순수 Kotlin 모듈 [`android/engine`](./android/engine) 에 있고 JUnit 으로 검증한다(SRS 킥테이블·7-bag·T-spin 판정·점수·좌표 등 §4·§13 데이터는 그대로 이식됨). 서버 계획(Cloudflare Workers + D1 + WebSocket)은 변경 없이 유지된다. 초기 웹(HTML) 프로토타입(`src/`, `index.html`)은 검증된 **동작 레퍼런스**로 남겨둔다.
+
 ---
 
 ## 무엇을 만드는가
diff --git a/android/.gitignore b/android/.gitignore
new file mode 100644
index 0000000..bb2de31
--- /dev/null
+++ b/android/.gitignore
@@ -0,0 +1,8 @@
+.gradle/
+build/
+*/build/
+local.properties
+.idea/
+*.iml
+captures/
+.cxx/
diff --git a/android/build.gradle.kts b/android/build.gradle.kts
new file mode 100644
index 0000000..749d414
--- /dev/null
+++ b/android/build.gradle.kts
@@ -0,0 +1,3 @@
+plugins {
+    kotlin("jvm") version "2.0.21" apply false
+}
diff --git a/android/engine/build.gradle.kts b/android/engine/build.gradle.kts
new file mode 100644
index 0000000..93a15b4
--- /dev/null
+++ b/android/engine/build.gradle.kts
@@ -0,0 +1,12 @@
+plugins {
+    kotlin("jvm")
+}
+
+dependencies {
+    testImplementation("junit:junit:4.13.2")
+}
+
+tasks.test {
+    useJUnit()
+    testLogging { events("passed", "failed", "skipped") }
+}
diff --git a/android/engine/src/main/kotlin/kr/tkrmagid/tetrig/engine/Engine.kt b/android/engine/src/main/kotlin/kr/tkrmagid/tetrig/engine/Engine.kt
new file mode 100644
index 0000000..29e68ed
--- /dev/null
+++ b/android/engine/src/main/kotlin/kr/tkrmagid/tetrig/engine/Engine.kt
@@ -0,0 +1,352 @@
+package kr.tkrmagid.tetrig.engine
+
+/**
+ * TETRIG 코어 엔진 (Kotlin 이식) — Phase 1.
+ * 순수 로직만: Android/렌더/타이머 의존 없음. UI 모듈이 타이밍을 구동한다.
+ *
+ * 좌표 규약 (명세서 §4.1):
+ *  - 보드 (x, y): x 오른쪽 증가, y 위쪽 증가. y=0 이 맨 아래.
+ *  - 킥 오프셋 (dx, dy): dy 양수 = 위쪽. 그대로 py += dy 로 적용.
+ *  - 회전 상태: 0=스폰, 1=CW, 2=180, 3=CCW.
+ *
+ * (웹 레퍼런스 src/engine.js 와 동일 알고리즘·데이터를 Kotlin 으로 이식)
+ */
+
+/** 튜닝 상수 (조정 대상은 여기 한 곳). */
+object Config {
+    const val BOARD_W = 10
+    const val BOARD_H = 40      // 내부 높이 (하단 20행만 표시)
+    const val VISIBLE_H = 20
+    const val NEXT_COUNT = 5
+    const val LOCK_DELAY_MS = 500
+    const val MAX_LOCK_RESETS = 15
+    const val DEFAULT_GRAVITY_MS = 800  // Phase 1 기본 (SPRINT)
+    const val DAS_MS = 133
+    const val ARR_MS = 10
+    const val SDF = 20
+}
+
+val PIECE_TYPES = charArrayOf('I', 'O', 'T', 'S', 'Z', 'J', 'L')
+
+/** 피스 색 (명세서 §13 v2 확정). 'G' = 가비지. */
+val PIECE_COLORS: Map<Char, String> = mapOf(
+    'I' to "#3EC1B6", 'O' to "#F5C531", 'T' to "#A76BF2", 'S' to "#7FCC4C",
+    'Z' to "#F25C4C", 'J' to "#4C7DF2", 'L' to "#F2913D", 'G' to "#46464F",
+)
+
+// ── 피스 스폰 셀 (박스-로컬, y 위쪽 증가) + 박스 크기 ──
+private data class Spawn(val box: Int, val cells: Array<IntArray>)
+
+private val SPAWN: Map<Char, Spawn> = mapOf(
+    'I' to Spawn(4, arrayOf(intArrayOf(0, 2), intArrayOf(1, 2), intArrayOf(2, 2), intArrayOf(3, 2))),
+    'O' to Spawn(2, arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(0, 1), intArrayOf(1, 1))),
+    'T' to Spawn(3, arrayOf(intArrayOf(0, 1), intArrayOf(1, 1), intArrayOf(2, 1), intArrayOf(1, 2))),
+    'S' to Spawn(3, arrayOf(intArrayOf(0, 1), intArrayOf(1, 1), intArrayOf(1, 2), intArrayOf(2, 2))),
+    'Z' to Spawn(3, arrayOf(intArrayOf(0, 2), intArrayOf(1, 2), intArrayOf(1, 1), intArrayOf(2, 1))),
+    'J' to Spawn(3, arrayOf(intArrayOf(0, 2), intArrayOf(0, 1), intArrayOf(1, 1), intArrayOf(2, 1))),
+    'L' to Spawn(3, arrayOf(intArrayOf(2, 2), intArrayOf(0, 1), intArrayOf(1, 1), intArrayOf(2, 1))),
+)
+
+/** 스폰 시 박스 원점의 보드 위치 (px, py). 셀은 (px+cx, py+cy). */
+private val SPAWN_POS: Map<Char, IntArray> = mapOf(
+    'I' to intArrayOf(3, 19), 'O' to intArrayOf(4, 21), 'T' to intArrayOf(3, 20),
+    'S' to intArrayOf(3, 20), 'Z' to intArrayOf(3, 20), 'J' to intArrayOf(3, 20), 'L' to intArrayOf(3, 20),
+)
+
+/** CW 회전: 박스 b 에서 (x,y) -> (y, (b-1)-x). */
+private fun rotateCW(cells: Array<IntArray>, b: Int): Array<IntArray> =
+    Array(cells.size) { i -> intArrayOf(cells[i][1], (b - 1) - cells[i][0]) }
+
+private fun buildStates(type: Char): Array<Array<IntArray>> {
+    val sp = SPAWN.getValue(type)
+    if (type == 'O') return arrayOf(sp.cells, sp.cells, sp.cells, sp.cells)
+    val s0 = sp.cells
+    val s1 = rotateCW(s0, sp.box)
+    val s2 = rotateCW(s1, sp.box)
+    val s3 = rotateCW(s2, sp.box)
+    return arrayOf(s0, s1, s2, s3)
+}
+
+/** STATES[type][state] = 셀 목록. */
+val STATES: Map<Char, Array<Array<IntArray>>> = PIECE_TYPES.associateWith { buildStates(it) }
+
+// ── 킥테이블 (명세서 §4.1) ──
+private val KICKS_JLSTZ: Map<String, Array<IntArray>> = mapOf(
+    "0>1" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(-1, 1), intArrayOf(0, -2), intArrayOf(-1, -2)),
+    "1>0" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(1, -1), intArrayOf(0, 2), intArrayOf(1, 2)),
+    "1>2" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(1, -1), intArrayOf(0, 2), intArrayOf(1, 2)),
+    "2>1" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(-1, 1), intArrayOf(0, -2), intArrayOf(-1, -2)),
+    "2>3" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(1, 1), intArrayOf(0, -2), intArrayOf(1, -2)),
+    "3>2" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(-1, -1), intArrayOf(0, 2), intArrayOf(-1, 2)),
+    "3>0" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(-1, -1), intArrayOf(0, 2), intArrayOf(-1, 2)),
+    "0>3" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(1, 1), intArrayOf(0, -2), intArrayOf(1, -2)),
+    // 180° (SRS+)
+    "0>2" to arrayOf(intArrayOf(0, 0), intArrayOf(0, 1), intArrayOf(1, 1), intArrayOf(-1, 1), intArrayOf(1, 0), intArrayOf(-1, 0)),
+    "2>0" to arrayOf(intArrayOf(0, 0), intArrayOf(0, -1), intArrayOf(-1, -1), intArrayOf(1, -1), intArrayOf(-1, 0), intArrayOf(1, 0)),
+    "1>3" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(1, 2), intArrayOf(1, 1), intArrayOf(0, 2), intArrayOf(0, 1)),
+    "3>1" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(-1, 2), intArrayOf(-1, 1), intArrayOf(0, 2), intArrayOf(0, 1)),
+)
+
+private val KICKS_I: Map<String, Array<IntArray>> = mapOf(
+    "0>1" to arrayOf(intArrayOf(0, 0), intArrayOf(-2, 0), intArrayOf(1, 0), intArrayOf(-2, -1), intArrayOf(1, 2)),
+    "1>0" to arrayOf(intArrayOf(0, 0), intArrayOf(2, 0), intArrayOf(-1, 0), intArrayOf(2, 1), intArrayOf(-1, -2)),
+    "1>2" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(2, 0), intArrayOf(-1, 2), intArrayOf(2, -1)),
+    "2>1" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(-2, 0), intArrayOf(1, -2), intArrayOf(-2, 1)),
+    "2>3" to arrayOf(intArrayOf(0, 0), intArrayOf(2, 0), intArrayOf(-1, 0), intArrayOf(2, 1), intArrayOf(-1, -2)),
+    "3>2" to arrayOf(intArrayOf(0, 0), intArrayOf(-2, 0), intArrayOf(1, 0), intArrayOf(-2, -1), intArrayOf(1, 2)),
+    "3>0" to arrayOf(intArrayOf(0, 0), intArrayOf(1, 0), intArrayOf(-2, 0), intArrayOf(1, -2), intArrayOf(-2, 1)),
+    "0>3" to arrayOf(intArrayOf(0, 0), intArrayOf(-1, 0), intArrayOf(2, 0), intArrayOf(-1, 2), intArrayOf(2, -1)),
+    // I 180°는 (0,0)만
+    "0>2" to arrayOf(intArrayOf(0, 0)), "2>0" to arrayOf(intArrayOf(0, 0)),
+    "1>3" to arrayOf(intArrayOf(0, 0)), "3>1" to arrayOf(intArrayOf(0, 0)),
+)
+
+private val ORIGIN = arrayOf(intArrayOf(0, 0))
+
+fun kickTable(type: Char, from: Int, to: Int): Array<IntArray> {
+    val key = "$from>$to"
+    return when (type) {
+        'O' -> ORIGIN
+        'I' -> KICKS_I[key] ?: ORIGIN
+        else -> KICKS_JLSTZ[key] ?: ORIGIN
+    }
+}
+
+/** 시드 가능 난수 (mulberry32) — JS 판과 동일 알고리즘. */
+fun makeRng(seed: Int): () -> Double {
+    var a = seed
+    return {
+        a += 0x6D2B79F5
+        var t = (a xor (a ushr 15)) * (1 or a)
+        t = (t + ((t xor (t ushr 7)) * (61 or t))) xor t
+        ((t xor (t ushr 14)).toLong() and 0xFFFFFFFFL).toDouble() / 4294967296.0
+    }
+}
+
+/** 7-bag. */
+class SevenBag(private val rng: () -> Double = { Math.random() }) {
+    private val q = ArrayDeque<Char>()
+    init { refill(); refill() }
+    private fun refill() {
+        val bag = PIECE_TYPES.toMutableList()
+        for (i in bag.indices.reversed()) {
+            val j = (rng() * (i + 1)).toInt()
+            val tmp = bag[i]; bag[i] = bag[j]; bag[j] = tmp
+        }
+        q.addAll(bag)
+    }
+    fun next(): Char {
+        if (q.size <= Config.NEXT_COUNT + 1) refill()
+        return q.removeFirst()
+    }
+    fun peek(n: Int = Config.NEXT_COUNT): List<Char> {
+        while (q.size < n) refill()
+        return q.take(n)
+    }
+}
+
+// ── 보드 유틸 ──
+typealias Board = Array<Array<Char?>>
+
+fun createBoard(w: Int = Config.BOARD_W, h: Int = Config.BOARD_H): Board =
+    Array(h) { arrayOfNulls<Char>(w) }
+
+fun pieceCells(type: Char, state: Int, px: Int, py: Int): Array<IntArray> {
+    val cells = STATES.getValue(type)[state]
+    return Array(cells.size) { i -> intArrayOf(px + cells[i][0], py + cells[i][1]) }
+}
+
+/** x 범위 밖 / 바닥 아래(y<0) / 점유 = 충돌. y >= H (버퍼 위)는 허용. */
+fun collides(board: Board, cells: Array<IntArray>): Boolean {
+    val w = board[0].size; val h = board.size
+    for (c in cells) {
+        val x = c[0]; val y = c[1]
+        if (x < 0 || x >= w || y < 0) return true
+        if (y < h && board[y][x] != null) return true
+    }
+    return false
+}
+
+/** 가득 찬 행 제거 후 위에서 빈 행 보충. 제거된 행 수 반환. */
+fun clearLines(board: Board): Int {
+    val w = board[0].size; val h = board.size
+    val rows = (0 until h).filter { y -> board[y].all { it != null } }
+    if (rows.isEmpty()) return 0
+    val rowSet = rows.toHashSet()
+    val kept = ArrayList<Array<Char?>>((0 until h).filter { it !in rowSet }.map { board[it] })
+    while (kept.size < h) kept.add(arrayOfNulls<Char>(w))
+    for (y in 0 until h) board[y] = kept[y]
+    return rows.size
+}
+
+fun isBoardEmpty(board: Board): Boolean = board.all { row -> row.all { it == null } }
+
+/** T-spin 판정 (명세서 §4.2). "none" | "mini" | "tspin". */
+fun detectTSpin(board: Board, type: Char, state: Int, px: Int, py: Int, lastMoveRotation: Boolean): String {
+    if (type != 'T' || !lastMoveRotation) return "none"
+    val w = board[0].size; val h = board.size
+    val cx = px + 1; val cy = py + 1
+    fun filled(dx: Int, dy: Int): Boolean {
+        val x = cx + dx; val y = cy + dy
+        if (x < 0 || x >= w || y < 0) return true   // 벽/바닥 = 채움
+        if (y >= h) return false                    // 버퍼 위 = 빔
+        return board[y][x] != null
+    }
+    val tl = filled(-1, 1); val tr = filled(1, 1); val bl = filled(-1, -1); val br = filled(1, -1)
+    val count = listOf(tl, tr, bl, br).count { it }
+    if (count < 3) return "none"
+    val front = when (state) {
+        0 -> Pair(tl, tr)
+        1 -> Pair(tr, br)
+        2 -> Pair(bl, br)
+        else -> Pair(tl, bl)
+    }
+    return if (front.first && front.second) "tspin" else "mini"
+}
+
+/** B2B 대상("어려운" 클리어): Quad 또는 라인 동반 T-spin 계열. */
+fun isDifficult(lines: Int, tspin: String): Boolean =
+    lines == 4 || (tspin != "none" && lines >= 1)
+
+data class LockResult(
+    val type: Char, val lines: Int, val tspin: String, val allClear: Boolean,
+    val combo: Int, val b2b: Int, val difficult: Boolean,
+)
+
+class Active(var type: Char, var state: Int, var x: Int, var y: Int)
+
+/** 게임 상태 (UI 가 타이밍을 구동). */
+class TetrigGame(seed: Int = 1) {
+    var board: Board = createBoard()
+        private set
+    private val bag = SevenBag(makeRng(seed))
+    var hold: Char? = null
+        private set
+    var holdUsed = false
+        private set
+    var over = false
+        private set
+    var lastMoveRotation = false
+    var lockResets = 0
+    var combo = -1
+        private set
+    var b2b = -1
+        private set
+    var lastClear: LockResult? = null
+        private set
+    lateinit var active: Active
+        private set
+
+    init { spawn() }
+
+    fun cells(a: Active = active): Array<IntArray> = pieceCells(a.type, a.state, a.x, a.y)
+
+    fun spawn(type: Char = bag.next()): Boolean {
+        val pos = SPAWN_POS.getValue(type)
+        active = Active(type, 0, pos[0], pos[1])
+        lastMoveRotation = false
+        lockResets = 0
+        if (collides(board, cells())) { over = true; return false }
+        return true
+    }
+
+    fun peekNext(n: Int = Config.NEXT_COUNT): List<Char> = bag.peek(n)
+
+    fun canFall(): Boolean {
+        val c = cells().map { intArrayOf(it[0], it[1] - 1) }.toTypedArray()
+        return !collides(board, c)
+    }
+
+    fun resetLockDelay(): Boolean {
+        if (lockResets >= Config.MAX_LOCK_RESETS) return false
+        lockResets++
+        return true
+    }
+
+    fun move(dx: Int): Boolean {
+        if (over) return false
+        val c = pieceCells(active.type, active.state, active.x + dx, active.y)
+        if (collides(board, c)) return false
+        active.x += dx
+        lastMoveRotation = false
+        return true
+    }
+
+    fun softDrop(): Boolean {
+        if (over) return false
+        val c = pieceCells(active.type, active.state, active.x, active.y - 1)
+        if (collides(board, c)) return false
+        active.y -= 1
+        lastMoveRotation = false
+        return true
+    }
+
+    /** dir: "cw" | "ccw" | "180". */
+    fun rotate(dir: String): Boolean {
+        if (over) return false
+        val a = active
+        val to = when (dir) {
+            "cw" -> (a.state + 1) % 4
+            "ccw" -> (a.state + 3) % 4
+            else -> (a.state + 2) % 4
+        }
+        for (k in kickTable(a.type, a.state, to)) {
+            val nx = a.x + k[0]; val ny = a.y + k[1]
+            if (!collides(board, pieceCells(a.type, to, nx, ny))) {
+                a.state = to; a.x = nx; a.y = ny
+                lastMoveRotation = true
+                return true
+            }
+        }
+        return false
+    }
+
+    fun ghostCells(): Array<IntArray> {
+        val a = active
+        var dy = 0
+        while (!collides(board, pieceCells(a.type, a.state, a.x, a.y - dy - 1))) dy++
+        return pieceCells(a.type, a.state, a.x, a.y - dy)
+    }
+
+    fun hardDrop(): LockResult? {
+        if (over) return null
+        val a = active
+        var d = 0
+        while (!collides(board, pieceCells(a.type, a.state, a.x, a.y - d - 1))) d++
+        a.y -= d
+        return lock()
+    }
+
+    fun holdSwap(): Boolean {
+        if (over || holdUsed) return false
+        val cur = active.type
+        if (hold == null) {
+            hold = cur
+            spawn()
+        } else {
+            val swap = hold!!
+            hold = cur
+            spawn(swap)
+        }
+        holdUsed = true
+        return true
+    }
+
+    fun lock(): LockResult {
+        val a = active
+        val tspin = detectTSpin(board, a.type, a.state, a.x, a.y, lastMoveRotation)
+        for (c in cells()) {
+            if (c[1] in board.indices) board[c[1]][c[0]] = a.type
+        }
+        val cleared = clearLines(board)
+        val allClear = cleared > 0 && isBoardEmpty(board)
+        combo = if (cleared > 0) combo + 1 else -1
+        val diff = isDifficult(cleared, tspin)
+        if (cleared > 0) b2b = if (diff) b2b + 1 else -1
+        val result = LockResult(a.type, cleared, tspin, allClear, combo, b2b, diff)
+        lastClear = result
+        holdUsed = false
+        spawn()
+        return result
+    }
+}
diff --git a/android/engine/src/test/kotlin/kr/tkrmagid/tetrig/engine/EngineTest.kt b/android/engine/src/test/kotlin/kr/tkrmagid/tetrig/engine/EngineTest.kt
new file mode 100644
index 0000000..60e9cf0
--- /dev/null
+++ b/android/engine/src/test/kotlin/kr/tkrmagid/tetrig/engine/EngineTest.kt
@@ -0,0 +1,204 @@
+package kr.tkrmagid.tetrig.engine
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class EngineTest {
+
+    private fun cellSet(cells: Array<IntArray>): Set<String> =
+        cells.map { "${it[0]},${it[1]}" }.toSet()
+
+    // ── 피스 상태/회전 ──
+    @Test fun tSpawnCells() {
+        assertEquals(setOf("0,1", "1,1", "2,1", "1,2"), cellSet(STATES.getValue('T')[0]))
+    }
+
+    @Test fun tCwState() {
+        // 오른쪽-포인팅: 세로줄 x=1 + (2,1)
+        assertEquals(setOf("1,0", "1,1", "1,2", "2,1"), cellSet(STATES.getValue('T')[1]))
+    }
+
+    @Test fun iCwState() {
+        assertEquals(setOf("2,0", "2,1", "2,2", "2,3"), cellSet(STATES.getValue('I')[1]))
+    }
+
+    @Test fun oNoRotation() {
+        val s0 = cellSet(STATES.getValue('O')[0])
+        assertEquals(s0, cellSet(STATES.getValue('O')[1]))
+        assertEquals(s0, cellSet(STATES.getValue('O')[3]))
+    }
+
+    @Test fun allPiecesHaveFourStates() {
+        for (t in PIECE_TYPES) assertEquals(4, STATES.getValue(t).size)
+    }
+
+    // ── 킥테이블 ──
+    @Test fun kickTablesMatchSpec() {
+        assertEquals("0,0 -1,0 -1,1 0,-2 -1,-2", kickStr(kickTable('T', 0, 1)))
+        assertEquals("0,0 -2,0 1,0 -2,-1 1,2", kickStr(kickTable('I', 0, 1)))
+        assertEquals("0,0 0,1 1,1 -1,1 1,0 -1,0", kickStr(kickTable('T', 0, 2))) // 180
+        assertEquals("0,0", kickStr(kickTable('I', 0, 2)))                        // I 180
+        assertEquals("0,0", kickStr(kickTable('O', 0, 1)))
+    }
+
+    private fun kickStr(k: Array<IntArray>) = k.joinToString(" ") { "${it[0]},${it[1]}" }
+
+    @Test fun wallKickUsesOffsetWhenBlocked() {
+        val g = TetrigGame(5)
+        // 엔진의 board 를 비우고, active 를 직접 배치할 수 없으니 collides 로 시나리오만 확인 후
+        // 실제 회전 킥은 별도 보드로 검증
+        val board = createBoard()
+        // (0,0) 회전(state1) 셀 중 (5,5)를 막고, (-1,0) 킥으로 성사되는지 검증
+        board[5][5] = 'X'
+        // state1 셀 at (4,5): pieceCells('T',1,4,5)
+        val blocked = collides(board, pieceCells('T', 1, 4, 5))
+        assertTrue(blocked)
+        val kicked = collides(board, pieceCells('T', 1, 3, 5)) // (-1,0)
+        assertFalse(kicked)
+    }
+
+    // ── 7-bag ──
+    @Test fun sevenBagContainsAllEachRound() {
+        val bag = SevenBag(makeRng(42))
+        repeat(20) {
+            val seven = (0 until 7).map { bag.next() }.sorted()
+            assertEquals(PIECE_TYPES.toList().sorted(), seven)
+        }
+    }
+
+    @Test fun peekMatchesConsumeOrder() {
+        val bag = SevenBag(makeRng(7))
+        val peek = bag.peek(5)
+        assertEquals(5, peek.size)
+        for (i in 0 until 5) assertEquals(peek[i], bag.next())
+    }
+
+    @Test fun sameSeedSameSequence() {
+        val a = SevenBag(makeRng(123)); val b = SevenBag(makeRng(123))
+        repeat(30) { assertEquals(a.next(), b.next()) }
+    }
+
+    // ── 충돌/클리어 ──
+    @Test fun collidesWallsFloorOccupied() {
+        val bd = createBoard()
+        assertTrue(collides(bd, arrayOf(intArrayOf(-1, 0))))
+        assertTrue(collides(bd, arrayOf(intArrayOf(10, 0))))
+        assertTrue(collides(bd, arrayOf(intArrayOf(0, -1))))
+        assertFalse(collides(bd, arrayOf(intArrayOf(5, 45))))
+        bd[3][4] = 'T'
+        assertTrue(collides(bd, arrayOf(intArrayOf(4, 3))))
+    }
+
+    @Test fun clearLinesRemovesFullAndDrops() {
+        val bd = createBoard()
+        for (x in 0 until 10) bd[0][x] = 'I'
+        bd[1][0] = 'T'
+        assertEquals(1, clearLines(bd))
+        assertEquals('T', bd[0][0])
+        for (x in 1 until 10) assertEquals(null, bd[0][x])
+    }
+
+    @Test fun boardEmpty() {
+        val bd = createBoard()
+        assertTrue(isBoardEmpty(bd))
+        bd[0][0] = 'I'
+        assertFalse(isBoardEmpty(bd))
+    }
+
+    // ── T-spin 판정 ──
+    @Test fun tspinFull() {
+        val bd = createBoard(10, 6)
+        bd[1][4] = 'X'; bd[1][6] = 'X'; bd[3][4] = 'X'
+        assertEquals("tspin", detectTSpin(bd, 'T', 2, 4, 1, true))
+    }
+
+    @Test fun tspinMini() {
+        val bd = createBoard(10, 6)
+        bd[1][4] = 'X'; bd[3][4] = 'X'; bd[3][6] = 'X'
+        assertEquals("mini", detectTSpin(bd, 'T', 2, 4, 1, true))
+    }
+
+    @Test fun tspinNoneTooFewCorners() {
+        val bd = createBoard(10, 6)
+        bd[1][4] = 'X'
+        assertEquals("none", detectTSpin(bd, 'T', 2, 4, 1, true))
+    }
+
+    @Test fun tspinNoneWhenNotRotation() {
+        val bd = createBoard(10, 6)
+        bd[1][4] = 'X'; bd[1][6] = 'X'; bd[3][4] = 'X'
+        assertEquals("none", detectTSpin(bd, 'T', 2, 4, 1, false))
+    }
+
+    @Test fun tspinFloorCountsAsFilled() {
+        val bd = createBoard(10, 6)
+        assertEquals("none", detectTSpin(bd, 'T', 2, 4, -1, true)) // 전면 2 + 뒤 0 = 2
+        bd[1][4] = 'X'
+        assertEquals("tspin", detectTSpin(bd, 'T', 2, 4, -1, true)) // 3 + 전면 완전
+    }
+
+    @Test fun difficultRule() {
+        assertTrue(isDifficult(4, "none"))
+        assertTrue(isDifficult(2, "tspin"))
+        assertTrue(isDifficult(1, "mini"))
+        assertFalse(isDifficult(3, "none"))
+        assertFalse(isDifficult(0, "tspin"))
+    }
+
+    // ── 게임 흐름 ──
+    @Test fun lockResetCappedAt15() {
+        val g = TetrigGame(1)
+        var ok = 0
+        repeat(25) { if (g.resetLockDelay()) ok++ }
+        assertEquals(Config.MAX_LOCK_RESETS, ok)
+    }
+
+    @Test fun spawnMoveHardDropCycle() {
+        val g = TetrigGame(3)
+        assertFalse(g.over)
+        val before = g.active.type
+        val res = g.hardDrop()!!
+        assertEquals(before, res.type)
+        assertNotNull(g.active)
+        assertFalse(g.holdUsed)
+    }
+
+    @Test fun holdOncePerPiece() {
+        val g = TetrigGame(9)
+        val first = g.active.type
+        assertTrue(g.holdSwap())
+        assertEquals(first, g.hold)
+        assertFalse(g.holdSwap())
+        g.hardDrop()
+        assertFalse(g.holdUsed)
+        assertTrue(g.holdSwap())
+    }
+
+    @Test fun comboAndB2b() {
+        val g = TetrigGame(2)
+        fun quad(): LockResult {
+            for (y in 0 until 4) for (x in 1 until 10) g.board[y][x] = 'X'
+            // I 세로(state1)를 col0에 정렬: x=-2 → 셀 x=2-2=0
+            val a = g.active
+            a.type = 'I'; a.state = 1; a.x = -2; a.y = 0
+            g.lastMoveRotation = false
+            return g.hardDrop()!!
+        }
+        val r1 = quad()
+        assertEquals(4, r1.lines)
+        assertEquals(0, r1.b2b)
+        val r2 = quad()
+        assertEquals(4, r2.lines)
+        assertEquals(1, r2.b2b)
+    }
+
+    @Test fun topOut() {
+        val g = TetrigGame(1)
+        for (y in 18 until 24) for (x in 0 until 10) g.board[y][x] = 'X'
+        assertFalse(g.spawn('T'))
+        assertTrue(g.over)
+    }
+}
diff --git a/android/gradle.properties b/android/gradle.properties
new file mode 100644
index 0000000..b430c7c
--- /dev/null
+++ b/android/gradle.properties
@@ -0,0 +1,3 @@
+org.gradle.jvmargs=-Xmx1536m
+org.gradle.caching=true
+kotlin.code.style=official
diff --git a/android/gradle/wrapper/gradle-wrapper.jar b/android/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..a4b76b9
Binary files /dev/null and b/android/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/android/gradle/wrapper/gradle-wrapper.properties b/android/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..e2847c8
--- /dev/null
+++ b/android/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/android/gradlew b/android/gradlew
new file mode 100755
index 0000000..f5feea6
--- /dev/null
+++ b/android/gradlew
@@ -0,0 +1,252 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s
+' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/android/gradlew.bat b/android/gradlew.bat
new file mode 100644
index 0000000..9b42019
--- /dev/null
+++ b/android/gradlew.bat
@@ -0,0 +1,94 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/android/settings.gradle.kts b/android/settings.gradle.kts
new file mode 100644
index 0000000..4ab1901
--- /dev/null
+++ b/android/settings.gradle.kts
@@ -0,0 +1,16 @@
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        google()
+        mavenCentral()
+    }
+}
+dependencyResolutionManagement {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+rootProject.name = "tetrig"
+include(":engine")
+// :app (Jetpack Compose UI) 모듈은 UI 단계에서 추가한다.