Add 2048 example (#6032)

## Summary

This PR adds [2048
game](https://en.wikipedia.org/wiki/2048_(video_game)) example.


https://github.com/software-mansion/react-native-reanimated/assets/20516055/db10f66c-707d-4442-959f-ee455fe62bd6

## Test plan

Just play the game.

---------

Co-authored-by: Bartłomiej Błoniarz <bartlomiej.bloniarz@swmansion.com>

apps/common-app/src/examples/Game2048Example.tsx

@@ -0,0 +1,331 @@
+import { Text, StyleSheet, View, ColorValue, Alert } from 'react-native';
+import Animated, { LinearTransition, ZoomIn } from 'react-native-reanimated';
+
+import React from 'react';
+import {
+  Gesture,
+  GestureDetector,
+  GestureHandlerRootView,
+} from 'react-native-gesture-handler';
+
+const N = 4;
+const TILE_SIZE = 72;
+const GAP = 10;
+const CELL_BORDER_RADIUS = 5;
+const CELL_BACKGROUND_COLOR = 'rgb(202,192,181)';
+const CELL_BORDER_COLOR = 'rgb(185,173,161)';
+
+interface Tile {
+  id: number;
+  row: number;
+  column: number;
+  value: number;
+  zombie: boolean;
+  hasJustBeenMerged: boolean;
+}
+
+enum Directions {
+  UP = 'up',
+  DOWN = 'down',
+  LEFT = 'left',
+  RIGHT = 'right',
+}
+
+let nextid = 1;
+
+function makeId(): number {
+  return nextid++;
+}
+
+function extractRow(tiles: Tile[], row: number): Tile[] {
+  return tiles.filter((tile) => tile.row === row);
+}
+
+function areTilesEqual(tiles1: Tile[], tiles2: Tile[]): boolean {
+  if (tiles1.length !== tiles2.length) {
+    return false;
+  }
+  sortTiles(tiles1);
+  sortTiles(tiles2);
+  for (let i = 0; i < tiles1.length; i++) {
+    if (
+      tiles1[i].id !== tiles2[i].id ||
+      tiles1[i].column !== tiles2[i].column ||
+      tiles1[i].row !== tiles2[i].row
+    ) {
+      return false;
+    }
+  }
+  return true;
+}
+
+function moveRowLeft(oldTiles: Tile[]): Tile[] {
+  if (oldTiles.some((tile) => tile.zombie)) {
+    throw new Error('Unexpected zombie tile');
+  }
+  const newTiles: Tile[] = [];
+  const oldTilesSortedByColumn = oldTiles.sort((a, b) => a.column - b.column);
+  let nextColumn = 0;
+  for (let i = 0; i < oldTilesSortedByColumn.length; i++) {
+    const thisTile = oldTilesSortedByColumn[i];
+    const nextTile = oldTilesSortedByColumn[i + 1];
+    if (nextTile !== undefined && thisTile.value === nextTile.value) {
+      // merge tiles
+      newTiles.push({ ...thisTile, column: nextColumn, zombie: true });
+      newTiles.push({ ...nextTile, column: nextColumn, zombie: true });
+      newTiles.push({
+        id: makeId(),
+        row: thisTile.row,
+        column: nextColumn,
+        value: thisTile.value * 2,
+        zombie: false,
+        hasJustBeenMerged: true,
+      });
+      i++; // skip next tile
+    } else {
+      newTiles.push({
+        ...thisTile,
+        column: nextColumn,
+        hasJustBeenMerged: false,
+      });
+    }
+    nextColumn++;
+  }
+  return newTiles;
+}
+
+function addRandomTile(oldTiles: Tile[]): Tile[] {
+  const MAX = N * N;
+  const taken = oldTiles.map((tile) => tile.row * N + tile.column);
+  const free = [...new Array(MAX)]
+    .map((_, i) => i)
+    .filter((i) => !taken.includes(i));
+  if (free.length === 0) {
+    throw new Error('No empty cells');
+  }
+  const idx = free[Math.floor(Math.random() * free.length)];
+  const row = Math.floor(idx / N);
+  const column = idx % N;
+  const value = Math.random() < 0.5 ? 4 : 2;
+  return oldTiles.concat({
+    row,
+    column,
+    value,
+    id: makeId(),
+    zombie: false,
+    hasJustBeenMerged: false,
+  });
+}
+
+function filterOutZombieTiles(tiles: Tile[]): Tile[] {
+  return tiles.filter((tile) => !tile.zombie);
+}
+
+function flipTilesVertically(tiles: Tile[]): Tile[] {
+  return tiles.map((tile) => ({ ...tile, column: N - 1 - tile.column }));
+}
+
+function transposeTiles(tiles: Tile[]): Tile[] {
+  return tiles.map((tile) => ({ ...tile, row: tile.column, column: tile.row }));
+}
+
+function transformTiles(
+  tiles: Tile[],
+  direction: Directions,
+  reverse: boolean
+): Tile[] {
+  switch (direction) {
+    case Directions.LEFT:
+      return tiles;
+    case Directions.RIGHT:
+      return flipTilesVertically(tiles);
+    case Directions.UP:
+      return transposeTiles(tiles);
+    case Directions.DOWN:
+      return reverse
+        ? transposeTiles(flipTilesVertically(tiles))
+        : flipTilesVertically(transposeTiles(tiles));
+  }
+}
+
+function makeMove(oldTiles: Tile[], direction: Directions): Tile[] {
+  oldTiles = transformTiles(oldTiles, direction, false);
+  let newTiles: Tile[] = [];
+  const aliveTiles = filterOutZombieTiles(oldTiles);
+  for (let row = 0; row < 4; row++) {
+    const oldRow = extractRow(aliveTiles, row);
+    const newRow = moveRowLeft(oldRow);
+    newTiles = newTiles.concat(newRow);
+  }
+  if (!areTilesEqual(aliveTiles, newTiles)) {
+    newTiles = addRandomTile(newTiles);
+  }
+  newTiles = transformTiles(newTiles, direction, true);
+  return sortTiles(newTiles);
+}
+
+function sortTiles(tiles: Tile[]): Tile[] {
+  return tiles.sort((a, b) => a.id - b.id);
+}
+
+function getTileBackgroundColor(value: number): ColorValue {
+  switch (value) {
+    case 2:
+      return 'rgb(236,228,219)';
+    case 4:
+      return 'rgb(234,224,202)';
+    case 8:
+      return 'rgb(232,180,129)';
+    case 16:
+      return 'rgb(231,154,109)';
+    case 32:
+      return 'rgb(230,130,102)';
+    case 64:
+      return 'rgb(228,104,71)';
+    case 128:
+      return 'rgb(232,208,127)';
+    case 256:
+      return 'rgb(231,205,113)';
+    case 512:
+      return 'rgb(231,201,100)';
+    case 1024:
+      return 'rgb(230,198,89)';
+    case 2048:
+      return 'rgb(230,195,79)';
+    default:
+      return 'rgb(60,56,50)';
+  }
+}
+
+function getTileForegroundColor(value: number): ColorValue {
+  return value <= 4 ? 'rgb(117,111,102)' : 'rgb(249,246,243)';
+}
+
+function getDirection(dx: number, dy: number) {
+  if (Math.abs(dx) > Math.abs(dy)) {
+    return dx > 0 ? Directions.RIGHT : Directions.LEFT;
+  } else {
+    return dy > 0 ? Directions.DOWN : Directions.UP;
+  }
+}
+
+function makeInitialBoard(): Tile[] {
+  return addRandomTile(addRandomTile([]));
+}
+
+function isBoardFull(tiles: Tile[]): boolean {
+  return filterOutZombieTiles(tiles).length === N * N;
+}
+
+function getPoints(tiles: Tile[]): number {
+  return filterOutZombieTiles(tiles).reduce((acc, tile) => acc + tile.value, 0);
+}
+
+export default function Game2048Example() {
+  const [tiles, setTiles] = React.useState(makeInitialBoard);
+  const [gameOver, setGameOver] = React.useState(false);
+
+  const fling = Gesture.Pan()
+    .runOnJS(true)
+    .onEnd((e) => {
+      if (gameOver) {
+        return;
+      }
+      const direction = getDirection(e.translationX, e.translationY);
+      const nextTiles = makeMove(tiles, direction);
+      setTiles(nextTiles);
+      if (isBoardFull(nextTiles)) {
+        setGameOver(true);
+        setTimeout(() => {
+          Alert.alert('Game over!', `${getPoints(tiles)} points`, [
+            { text: 'Play again', onPress: handleReset },
+          ]);
+        }, 500);
+      }
+    });
+
+  const handleReset = React.useCallback(() => {
+    setTiles(makeInitialBoard());
+    setGameOver(false);
+  }, []);
+
+  return (
+    <GestureHandlerRootView style={styles.container}>
+      <GestureDetector gesture={fling}>
+        <View style={styles.board}>
+          {[...new Array(N)].map((_, row) => (
+            <View key={row} style={styles.row}>
+              {[...new Array(N)].map((_, column) => (
+                <View key={column} style={styles.cell} />
+              ))}
+            </View>
+          ))}
+          {tiles.map((tile) => (
+            <Animated.View
+              style={[
+                styles.tile,
+                {
+                  top: tile.row * (TILE_SIZE + GAP) + GAP,
+                  left: tile.column * (TILE_SIZE + GAP) + GAP,
+                  zIndex: tile.zombie ? 1 : 2,
+                  backgroundColor: getTileBackgroundColor(tile.value),
+                },
+              ]}
+              entering={
+                tile.hasJustBeenMerged
+                  ? ZoomIn.springify(200).dampingRatio(0.6).delay(150)
+                  : ZoomIn.duration(150).delay(150)
+              }
+              layout={LinearTransition.duration(120)}
+              key={tile.id}>
+              <Text
+                style={[
+                  styles.value,
+                  { color: getTileForegroundColor(tile.value) },
+                ]}>
+                {tile.value}
+              </Text>
+            </Animated.View>
+          ))}
+        </View>
+      </GestureDetector>
+    </GestureHandlerRootView>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+  },
+  board: {
+    backgroundColor: CELL_BORDER_COLOR,
+    borderRadius: GAP,
+    padding: GAP,
+    gap: GAP,
+    position: 'relative',
+  },
+  row: {
+    flexDirection: 'row',
+    gap: GAP,
+  },
+  cell: {
+    backgroundColor: CELL_BACKGROUND_COLOR,
+    borderRadius: CELL_BORDER_RADIUS,
+    width: TILE_SIZE,
+    height: TILE_SIZE,
+  },
+  tile: {
+    width: TILE_SIZE,
+    height: TILE_SIZE,
+    borderRadius: CELL_BORDER_RADIUS,
+    alignItems: 'center',
+    justifyContent: 'center',
+    position: 'absolute',
+  },
+  value: {
+    fontSize: 35,
+    fontWeight: 'bold',
+  },
+});

apps/common-app/src/examples/index.ts

@@ -45,6 +45,7 @@ import FlatListExample from './SharedElementTransitions/FlatList';
 import FlatListSkipEnteringExiting from './LayoutAnimations/FlatListSkipEnteringExiting';
 import FrameCallbackExample from './FrameCallbackExample';
 import GalleryExample from './SharedElementTransitions/Gallery';
+import Game2048Example from './Game2048Example';
 import GestureHandlerExample from './GestureHandlerExample';
 import GetViewPropExample from './GetViewPropExample';
 import IPodExample from './IPodExample';
@@ -410,6 +411,11 @@ export const EXAMPLES: Record<string, Example> = {
     title: 'Chessboard',
     screen: ChessboardExample,
   },
+  Game2048Example: {
+    icon: '🕹️',
+    title: '2048',
+    screen: Game2048Example,
+  },
   OverlappingBoxesExample: {
     icon: '🔝',
     title: 'z-index & elevation',