Ball Sort — sorting balls by test tube
You move glass balls between test tubes until each one contains a single color. The first tap picks up the top ball, the second drops it into another test tube. The rule is the same as in Sorting Balls: you can only place a ball into an empty test tube or onto a ball of the same color.
The main challenge here is groups. If there are two or three balls of the same color on top, they move together. A group only splits if there isn’t enough space in the new test tube. How many balls fit depends on the tube’s height. So one move can use up all the free space and block the color you were trying to reach.