For the open source category, you'll need to have a README file and License file.
Great foundation for your game. Would be great to add some music and sound effects. Interesting that you chose to have mouse controls only. Would also be good to have the timer/tempo/score on screen so the player has something they'd like to target to. You could also add an element of increasing difficulty by adding an element of change to the balance beam; ie. items falling, changing gravity, changing length of beam etc. Nice work.