Devil-Doku

One devil per row, per column and per coloured region — and never touching. A dark little logic puzzle that climbs from 5×5 all the way to 12×12, wicked.

Mark up a square with an ✕ to rule it out, or drop in a devil where you're sure one belongs. No two devils may touch, not even corner to corner — work the rows, the columns and the coloured regions until only one square is left for each. Every board has exactly one answer and can always be reasoned out; you never have to guess.

Three mistakes ends a run. A flawless board scores triple a two-mistake one, so care beats speed — finish under par and the leftover seconds are added on top.

Play Mischief to climb slowly (every size twice before it grows), or Diabolical to step up a size with every win. Or pick a size on its own from Size and practise outside a run.