Each colour has a nucleus and a bunch of shapes trying to protect it. Shapes automatically spread out around the nucleus and will attack enemy shapes on contact.
When the nucleus is destroyed, the player is defeated. The last player left wins.

New shapes are created by marbles falling into relevant triggers.
The marbles can also increase the player's number, which determines number of shapes to spawn (for circles, triangles and squares) or the size and power level of the shape (for pentagons and hexagons).

Shapes:
Circle Doesn't do anything special.
Triangle Has high attack damage, and automatically moves towards enemies. Does not stay near the nucleus.
Square Reflects incoming projectiles.
Pentagon Deals splash damage and follows enemies.
Hexagon Shoots a high damage projectile.

Who will win?

Patreon:   / lostmarbleruns  
Discord:   / discord  

Thanks to Muffinskill on Patreon for the name suggestion.