You are standing on a platform upon which meteors are falling down. Every meteor that hits destroys parts of the platform, so bit by bit you're running out of space.
That being said, you can repair those holes and pick ups give you boosts to aid you in your survival. Half of them are bad for you, though.

Controls:
WASD or arrow keys to move
Esc to pause the game
Space bar to create a tile

Unfortunately the game has a bug which makes the level collapse, and I probably cannot fix it in the remaining time, and there are a couple other mistakes, but I'm happy with the result (and the process) nonetheless for my first game jam.

I used Unity for this. Some of the audio files I created on my own by using as3sfxr, some were taken from Unity's asset store. The UI elements are also taken from the asset store ("Unity Sample UI").