I. Core Operation
Control Method: Single-finger touch. Tap any test tube to select it, then tap the target test tube to move the topmost ball from the selected tube to the target.
Movement Rules: Balls can only be placed on top of same-color balls. The target tube must have remaining space (max 4 balls) — different-colored balls cannot be stacked.
II. Game Objective
Sort all balls in the test tubes (with no time limit or within a specified time) — gather 4 balls of the same color into one tube. Complete sorting all colors to clear the level and unlock the next!