After I dropped my first idea, I started with a Osmos-style game. Going pretty well so far, bigger mobs can absorb smaller mobs, the player can move around, zooming is implemented and automatic scrolling as well.

Next up:

• Power-Ups (Mobs with other colors, increasing your speed etc.)
• First sound effects
• Automatic zooming when player gets bigger
• Boundaries, mobs should knock back
• “Unabsorbable” mobs (other mobs than the player should not be able to absorb power ups)
• And food! Oh god, I’m hungry.