Build your robot by picking up pieces of junk and attaching them to other pieces of junk.
Some pieces of junk can be controlled by pushing the key shown when the piece is moused over. The key can also be rebound by right clicking a piece.
Once you have added assembled your masterpiece, press space to launch it, and control it with the previously assigned piece keys.
Make it to the end or press space again to return to the drawing board and try again.
Good luck!

Sebastian Parfitt – Game Design + Programming
David Hubber – Game Design  + Programming
Jonas Braukmann – Game Design, Graphics + Music

The Global Game Jam web page got more details so here you go: