龜速快手

Every row, every column and every colour on the board holds exactly one turtle, and your job is to work out where each one goes. The rules take a moment to learn; the puzzles take a little longer, with thousands of levels that climb from gentle warm-ups to boards that need real deduction, plus special shaped grids that break out of the usual squares. When you get stuck, cross off the squares that cannot work and the answer slowly appears. It runs in your browser on phone or PC, free.