fix rotation

app/nose/bin/tetris.ts

@@ -174,9 +174,7 @@ export function update(_delta: number, input: InputState) {
   const keys = input.pressed
 
   if (input.justPressed.has(" ")) {
-    player.rotation += 1
-    if (player.rotation === SHAPES[player.shape]!.length)
-      player.rotation = 0
+    rotateShape()
   }
 
   // tetris animation
@@ -455,4 +453,26 @@ function drawPreview(game: GameContext) {
       drawBlock(game, previewX + col + offsetX, previewY + row + offsetY, COLORS[nextShape.shape]!)
     }
   }
-}
+}
+
+function rotateShape() {
+  const oldRot = player.rotation
+  const newRot = (oldRot + 1) % SHAPES[player.shape]!.length
+
+  if (!collision(player.x, player.y, newRot)) {
+    player.rotation = newRot
+    return
+  }
+
+  if (!collision(player.x + 1, player.y, newRot)) {
+    player.x += 1
+    player.rotation = newRot
+    return
+  }
+
+  if (!collision(player.x - 1, player.y, newRot)) {
+    player.x -= 1
+    player.rotation = newRot
+    return
+  }
+}