Perimeter is a radial wave shooter. Your core sits fixed in the middle of the arena and enemies spiral inward from every direction at once. You do not move — you rotate. The turret fires continuously in whatever direction you are pointing, so the entire game is a question of where to look and when to look somewhere else.
That constraint is what makes it interesting. In a normal shooter you can retreat. Here the arena has no corners and no cover, and every second you spend clearing one side is a second the other side gets closer.
Controls
Move your pointer, or drag on a touchscreen, and the turret aims where you point. On a keyboard, the left and right arrows (or A and D) rotate it. You never need to press fire — the turret fires on its own, roughly eight shots a second.
The waves
Each wave sends more enemies, with more health, moving faster and spawning closer together than the last. Enemies do not travel straight at you: each one carries a slight orbital drift, so they arrive on a curve. Every fourth wave ends with a boss — a much larger, slower target with a visible health bar that soaks a sustained burst.
You do not move. You rotate.
Scoring
- Enemy destroyed — 20 points, multiplied by your current chain (up to ×10).
- Boss destroyed — 500 points, also multiplied by the chain.
- Wave cleared — 100 points × the wave number, so surviving deep is worth far more than farming early.
- The chain counts consecutive kills and resets whenever you take a hit — which is the real cost of being hit, more than the life itself.
Lives
Three. An enemy reaching your core costs one and gives you about a second of invulnerability to recover your aim. Lose all three and the run ends.
Playing against someone
Everybody gets the identical wave composition and spawn angles on a given day, so a challenge link puts your friend in exactly the arena you just died in.