Objective
Take turns choosing an unused number that is a factor or a multiple of the last number played. The player who cannot move loses, so the last successful move wins.
Factors and multiples
- A factor of 12 includes 1, 2, 3, 4, 6 and 12.
- A multiple of 12 on a 1 to 50 grid includes 12, 24, 36 and 48.
- 1 is a factor of every number, so 1 is always legal while it is still unused.
- Once 1 is taken, every remaining number is a multiple of 1, so the rest of the grid can be claimed in any order.
First move
In practice you pick any unused number to start. In the daily game a shared starting number is already taken, so you move second from that last number. You always play the computer, not another person.
Controls
- Tap a number with a red outline to play it.
- An illegal tap is rejected and the number stays unused.
- Hint plays one legal move for you. Undo takes back your last move and the computer reply.
Difficulty
- Easy: 1 to 50
- Classic: 1 to 75
- Hard: 1 to 100
Daily challenge
Everyone receives the same 1 to 100 start. It resets at midnight UK. The first win of the day counts for the league and your streak.