Simple Tetris implementation. Let me write clean code with a canvas, an 10x20 grid, 7 tetrominoes using SRS-like kicks (simple wall kicks), a next-piece preview, score/lines/level, gravity that speeds up with level, soft-drop score, hard-drop, line clearing, game over, and restart with Enter/R.

Implement pieces with a rotation state array or rotation via matrix rotation. Simpler: define pieces as coordinate sets, rotate with a matrix rotation function, and try a set of simple wall kicks [0, -1, +1, -2, +2].

Alright, let's write the file.