Alien tetrominoes are marching down on you. A new row arrives every few seconds - the bar along the ceiling shows how long until the next march.
Drag anywhere (or use the arrow keys / A and D) to slide your cannon. It fires automatically, and the glowing column guide shows exactly which block your shot will hit.
Each shot destroys the lowest block in its column. Armoured grey blocks take two hits, bomb blocks blast a 3x3 area, and star blocks always drop a power-up.
Clear a whole row for a LINE bonus that also delays the next march. Destroy every block of a piece for a PIECE bonus.
Keep your hit streak alive. Shots into an empty column are misses and reset your multiplier (up to x5).
If a block reaches the red line it is a breach. You lose a life and the bottom rows are blasted away. Lose all 3 lives and it is game over.
OPTIONS switches between Classic, Rush (75 seconds) and the Daily Challenge, changes fire mode and skins, and shows the leaderboards, trophies and bug reporting.