This is actually one of my prettiest games in competitions, and it plays very nicely too…
The theme was “Beneath the Surface”, so I made a game where the player controls a mining ship for gaseous super-giant planets…
The deeper you go, the more pressure damage you take, so you have to balance the risk: you need to mine resources, which you have to spend to repair the damage, and you have to go deeper to get more resources!
The levels were all procedural, which added to the variety, and the ship controlled a bit like “Moon Lander”, with a lot of inertia and gravity.
You can download for free the full game and the source code.