Drop tetrominoes like Tetris. The board has two parts: a staging band at the top that never rotates, and the square arena below it (pick 9×9, 10×10, or 11×11 from the menu). New pieces appear in the staging band — slide them left/right to line up your drop before they fall into the arena. If the stack ever backs up so a square is stuck in the staging band, it's game over.
Each brick has one of 3 colours and a shape on this ladder: ■ → ● → ▲ → 💣. At level 1, falling pieces carry only squares and circles (80% / 20%). As levels rise the deals get richer — triangles appear, and by level 10 about 1 in 10 tetroids even carries a charged 💣.
One rule, repeated: match 3 or more bricks of the same colour and shape touching (any direction) — they squash into one brick of the next shape.
3 triangles make a 💣 bomb. Bombs are the only bricks with a number: a new bomb's charge equals the size of the triangle cluster that made it, shown as a fill level. Bombs match by 3 as well, and their charges add up.
Bombs explode two ways:
Tap a bomb (any time you can act) to detonate it early: it blasts its 8 neighbouring cells and sweeps a few of its colour's bricks from the field — up to 1 at charge 3, up to 3 at charge 4, then 5/7/9/11 at charges 5–8, and never more than 33% / 50% / 70% of that colour respectively. Smaller shapes vanish at a much higher ratio, so ■ go first and your evolved bricks mostly survive. A tapped bomb leaves inert gray rubble where it stood.
Or grow it: a bomb reaching charge 9 explodes on its own and leaves no rubble — sweeping 80% of its colour at charge 9, 90% at 10, and 100% at 11 or more, plus the 8-cell blast. Patience buys a bigger, cleaner boom; tapping buys control now but clears less and pollutes.
Sweeps never touch other bombs. A bomb only goes off if the blast reaches it — a bomb caught in a neighbouring explosion doesn't just vanish, it chain-explodes with its own sweep and blast, leaving rubble like a tapped bomb. Chains clear enormous amounts, but every link adds rubble — clean sweeps come only from charge-9 bombs.
Rubble never matches and never leaves on its own — the only way to remove it is to catch it in the blast of a later explosion. So tapped bombs both clear and pollute: aim them well, and use new blasts (or clean charge-10 booms) to sweep up old rubble.
Rotation is optional. Since clusters merge on contact in any direction, you often won't need it — skip to drop the next piece as-is. When you do rotate, gravity swings 90° and the whole arena slides to the new floor, reshuffling the pile so separated squares can fall together into new clusters and chains. During the rotate step, the board shows ⟲ ↓ ⟳ with a countdown; if it hits zero, the game skips automatically.