The pattern shows once. Rebuild it.
Watch. Each round, a pattern of tiles flashes in phosphor violet, then goes dark. Round 1 shows 3 tiles for 2.5 seconds; by round 10 it is 10 tiles at 1.5 seconds.
Rebuild. Tap cells to mark where the tiles were. When you have marked exactly the right number, press Reveal (or Enter). Green = correct, violet = a tile you missed, red ✕ = a wrong pick.
One mistake ends the run. Your score is the number of perfect rounds. 10/10 is a perfect eidetic day.
Keyboard: arrow keys move the cursor, Space toggles a mark, Enter reveals when armed.
Accessibility note: Afterimage is inherently a timed game — the brief flash is the puzzle, so it stays timed even under reduced motion (we only remove decorative transitions and make the fade instant). If the default view times are too fast, use the +50% view time toggle below the grid; extended runs are marked with ⏱ in the shared result but still count for streaks and stats.
Everyone gets the same 10 patterns each day. Your first run of the day is your recorded score; replays are labeled practice and do not touch stats.
Afterimage keeps memory pure: spatial recall, ten escalating flashes, one shared daily seed, one mistake and the lights stay off.
Entirely static and client-side — there is no server. The date is the server: today's date seeds the same ten patterns for everyone, everywhere.