You fly a little ship along the bottom of the screen. Slide a finger left and right anywhere on the play area to move — the ship fires upward automatically, so you can keep both eyes on dodging. Up top, a swarm of aliens sways from side to side. Every so often one or more peel off and swoop down at you in curving dives, dropping bombs as they come. Shoot the whole swarm to clear the wave; the next wave dives sooner and faster.
It's a modern take on the fixed-shooter arcade classics — Galaxian, Space Invaders and the Acorn Electron favourite Arcadians. Aliens still in formation are worth points; the ones diving at you are worth double, but they're the ones that can crash into you or bomb you. You get a few lives, and a short moment of invulnerability after each hit. Your best score is saved on your device.
How many players? One. It's a solo high-score chaser — pass the phone to take turns.
What are the controls? Just touch — slide to move, and the ship shoots on its own. On a keyboard you can also use the arrow keys.
How do I win? There's no end — survive as long as you can and beat your best score.
Does it need signal? No. Once the page has loaded once, it works fully offline.