Tetrominoes

Goal of the game

Four-block pieces fall into a well 10 columns wide. Move them and rotate them to complete horizontal lines, which disappear. The game ends when the blocks overflow the top of the well.

Keyboard controls

• ← → or A D: move (hold to slide).
• ↑, X or W: rotate clockwise; Z or Ctrl: counterclockwise.
• ↓ or S: soft drop; Space: hard drop.
• C or Shift: hold a piece; P or Esc: pause.

Touch controls

• Slide your finger left or right: the piece follows your finger.
• Tap the right half of the screen to rotate clockwise, the left half to rotate counterclockwise.
• Swipe down to lower the piece, with a sharp flick for the hard drop; swipe up to hold.
• The button bar at the bottom offers the same actions.

Modern rules

• Pieces come in bags of seven: each shape comes back at least once in every seven draws.
• The ghost piece shows where the piece will land. The hold can be used once per piece.
• Lock delay: a piece that has landed can still slide or rotate for half a second (fifteen times at most).
• Rotation with kicks: a blocked piece tries several neighbouring positions, which makes T-spins possible.

Scoring

Single 100, double 300, triple 500, quadruple 800, multiplied by the level. A T-spin (a T piece rotated into a cavity with three corners) is worth a lot more. Back-to-back difficult clears and combos add bonuses. The level goes up every ten lines.

Duel against the AI

Each clear sends garbage lines to your opponent: double 1, triple 2, quadruple 4, T-spin double 4, plus combos and back-to-backs. Incoming lines build up in the red gauge and rise as soon as you lock your next piece without clearing; clearing lines cancels them first. The first to overflow loses.

About the AI

The AI enumerates every reachable placement (including the hold), then scores each board using the criteria of Dellacherie's El-Tetris algorithm: landing height, lines cleared, row and column transitions, holes and wells. At the Intense and Infernal levels, it also looks ahead to the next piece. Lower levels add noise to the evaluation and react more slowly. The computation runs in a separate thread.