RotaStone vs Feynman rules

RotaStone is a fun and addictive, very difficulut puzzle game! Use rotation switches to place stones into colored hexes as same as stone's color. The difficulty level increases progressively as the level goes up. Can you clear all the levels? ◇ How to play: - Tap the rotation switch to rotate the stones around the stone. - When you tap the rotation switch, the stones placed around it will rotate around the rotation switch. - When all colored hexes have stones of the same color, the level is cleared. ◇ Features: - One-finger controls - Various unique stages - No penalties! No time limit! You can enjoy it at your own pace.

This app introduces Feynman rules. You can get some understanding for Feynman diagrams. E is external point, V is vertex, P is propagator, and S is symmetry factor.