Tetris

Build a playable falling-block Tetris game on a canvas with a 10-column, 20-row visible board. Use HTML, CSS, and JavaScript as needed. Write it to `index.html` in the current working directory using your file tools. Inline your own CSS and JavaScript. Do not use external assets, CDNs, or network requests. No third-party libraries are provided. Required behavior: - Include all seven tetrominoes with legal spawn positions. Use Left/Right to move, Up to rotate clockwise, Down to soft-drop, and Space to hard-drop. Show the controls. - Reject moves and rotations that overlap occupied cells or leave the board. Wall kicks are optional; if unsupported, reject the blocked rotation without changing the piece. - Lock landed pieces, clear complete rows, move rows above downward, and spawn the next piece. Display score, cleared-line count, level, and a next-piece preview. - Award 100, 300, 500, or 800 points for clearing one, two, three, or four rows with one piece, multiplied by the current level. Start at level 1 and increase gravity speed every ten cleared lines. - If a new piece cannot spawn, show Game Over. Provide Pause/Resume and Restart, with restart resetting the board, score, level, and piece sequence state. Hold and ghost pieces are optional. Verify: Move and rotate the first piece, then hard-drop it. Check that it locks into the board, a new piece spawns, and the next-piece preview advances. Pause and resume, then use Restart and check the cleared board, score, and level.