Zero or O: free online game
Zero or the letter O? An observation game where a single character differs from the rest. Easy to understand, hard to finish fast.
Play Zero or OFree, zero ads, no sign-up, on mobile and desktop.
How to play
A letter “O” is hiding among the zeros. Find it, round after round.
What this game trains
- Attention and focus: quickly pick out the right item among distractors.
Levels
Easy · Hard · Expert · Hardcore — each level has its own leaderboard.
Challenge your friends
At the end of a game, send your score as a link: your friend plays exactly the same puzzle and you compare your times. There is also a daily challenge and tournaments.