The outbreak is loose in the streets and your only tool is a wall. Quarantine Zombies has you trace barriers across city blocks until every zombie on the level is sealed inside a small zone, and new ones keep showing up if you take too long.
On a keyboard you steer with the arrow keys and lay wall as you move; Space starts or retries, P pauses and R restarts. On a phone you swipe to steer. A run ends when a zombie touches you, when one reaches a wall you have not finished, or when you cross your own fresh wall.
Steering a line that must never cross itself will feel familiar to anyone raised on Classic Snake.