Prime Sieve — free browser game

Prime Sieve is an original arcade that blends fast mental primality checking with reflex. Number discs fall from the top in 5 columns (starting from 2, ranging up to 99 as the run progresses). Your job is to act as a literal prime sieve (Sieve of Eratosthenes): catch the COMPOSITE numbers by clicking or tapping — e.g. 4, 6, 8, 9, 10, 12, 15, 16, 21, 25, 27, 33, 49, 51, 77, 91. Each correct catch is +1 score with a brief green pulse. Tapping a PRIME (2, 3, 5, 7, 11, 13, 17, 19, 23, 29…) is a sieve fault and costs a life — primes are supposed to fall through naturally. If a COMPOSITE makes it to the floor, the sieve leaked and you lose a life too. You start with three lives; when they're gone the run ends and your local best is saved. Keyboard shortcut: keys 1–5 catch the lowest disc in that column — clicking on desktop and tapping on mobile also work. Fall speed and spawn density rise with your score, and the value range grows into two-digit numbers as you progress. Strategy: when in doubt, don't tap — letting an unclear disc drop costs nothing if it's prime; deal with obvious multiples of 2 and 5 first to keep the playfield sparse; the trickiest composites are multiples of 7, 11 and 13 hiding near the √n threshold (think 49, 77, 91).