PRIME CATCHER
Spot the primes.
Clear them.
Numbers fall. Tap only the primes. Primes you haven't learned yet glow to help you — after five encounters the glow stops, and it's down to your number sense.
HOW TO PLAY
One rule to learn.
Tap the primes. Everything else stacks up. Reach the red line and it's over.
Numbers fall
Number blocks with 1 to 4 digits drop in. Only primes you haven't learned yet glow — the glow fades after five encounters. Stack up to the red line and it's over.
Tap a prime
Think it's a prime? Tap it. Get it right and it clears for points. Once you've learned a prime it stops glowing — then it's all you.
Wrong tap = penalty
51 = 3 × 17. Tap a non-prime and a penalty row falls across all seven columns. Your streak breaks too.
SPECIAL NUMBERS
More than prime-spotting.
Numbers with a mathematical story show up in gold. Clear a row with one to bank it, then tap it when you need it most — except 341, which protects you just by being in hand.
"Grothendieck prime"
57 = 3 × 19A composite the great mathematician allegedly offered as an example of a prime. Re-lights the prime hints for 19 seconds.
Smallest Fermat pseudoprime (base 2)
341 = 11 × 31The smallest "fake prime" that fools the base-2 Fermat test. Held in hand, it absorbs one wrong tap and saves your streak.
Taxicab number
1729 = 1³+12³ = 9³+10³Ramanujan's taxicab number. A cleaning taxi roams the board for ~19 seconds, clearing the cells it drives through.
The composite that looks prime
91 = 7 × 13A number few spot as a multiple of 7. For 13 seconds every block falls at half speed.
Smallest Carmichael number
561 = 3 × 11 × 17It fakes primality for every base coprime to it. Clears the prime-numbered columns (2nd, 3rd, 5th, 7th) top to bottom.
Chains clear space, not points. Catch a prime, blocks above drop, and a row of non-primes vanishes. Chains score nothing — they buy you room and a chance at a special number. Your multiplier comes from your longest streak of correct taps.
TURNING UP THE HEAT
It only stays calm at first.
Play on and the board starts pushing back. Keep your head, or get buried.
Prime Rush
Clear every block off the board and get six seconds of nothing but primes. All yours — if your fingers keep up.
Prime storms
After a lull, a storm is announced and hits. One of eight, chosen at random — all primes, almost none, a fast drifting wall, or sheer volume. The higher the level, the more often storms hit, and the harder.
→ 10
Stars into specials
Catch related primes — twins, cousins — and stars add up; clearing rows adds them too. Seven stars the first time, ten after that, and a special number falls onto the board. Clear its row to bank it.
ONLINE RANKING
Climb to world #1.
Last-30-days and all-time leaderboards. The one-minute Sprint puts everyone under the same rules — no hints, no gifts, and exactly one 341 hidden in the opening rain. Sixty seconds to clear all you can.
- Sprint (1 min) — same rules for everyone, no hints.
- Practice mode — drill exactly the numbers you trip over.
- Light / dark — color-blind-friendly palettes.
PRACTICE
Drill only what
you got wrong.
Every number you miss is remembered, and Practice serves exactly those back to you. Next time it falls, you won't hesitate.
PRIME ENCYCLOPEDIA
All 1,229 primes,
2 to 9973.
Each one comes with a bite-sized fact. The encyclopedia fills in as you play — learning that actually sticks.
GET THE GAME
Start free.
Free to play, zero ads during gameplay. No pay-to-win items, no rewarded ads — skill is the only edge. Want to support? One-time packs, priced so that dropping the zeros leaves a prime.
iPhone and iPad.
The seven-column board scales with the screen. Portrait only — one hand or two.
Available in Japan, the US, the UK, Switzerland and more (EU: in preparation).
iOS first. Prices are shown in yen; the App Store charges the equivalent in your local currency.
SPECIAL THANKS
Your name and your number.
Prime Fan puts your name and a composite of your choice on the composite shelf; Prime Master puts your name and a prime on the prime shelf — first come, first served, in the app and on this website. Master adds a message and a link.
Remove Ads
Drop the zero: 43 — prime
Removes all ads.
Prime Fan
Drop the zero: 173 — prime
Ad-free, plus your name and a composite of your choice.
Prime Master
Drop the zeros: 101 — prime
Ad-free, plus your name, a prime of your choice, a message and a link.