Chubby Finn

Sokoban with a seal. Chubby Finn pushes beach balls across a grid of ice tiles onto marked targets, four directions, one square at a time, and nothing can ever be pulled back. The whole difficulty of the form lives in that rule: a ball shoved into a corner is finished, and so is the level. Later boards add more balls than you have room to maneuver and force you to work out the order before touching anything. Short levels, instant restart, no time pressure at all.