Some ideas (out of the usual ones as temporary powerups, upgrades, missions, etc.):
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The player must try to stabilize the platform (eliminating more enemies from one side or other). If the platform is very unballanced, the platform will fall off and lose the level.
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More obstacles, and with different effects if you touch them with blue or red color (bouncing, strenght, gravity…).
The game has a lot of possible actions and mechanics. And one button (perfect for mobile screens). You have something here ;)