Radix

Pour liquid between tubes until the rack sorts itself out. No timer, no rush, and never a board that cannot be solved.

Lift a tube, pour it onto a matching colour, and watch the rack get simpler. A pour takes the whole run of one colour at once, so the move you want is usually bigger than the one you were about to make.

Two spare tubes are all the working room you get. Every board is checked by a solver before it is dealt, so there is always a way through — and if you pour yourself into a corner, the board says so and an undo takes it back. Undos are a pool, though, and when it is empty a closed board is the end of the run.