The rules are a modified version of ‘Around the world’. You must hit 1-20 consecutively, and cannot move to the next number until you have hit the current number your on. First aim using the mouse, left and right, then click and hold the mouse to get the power you want. The darker green bar (appears after your first shot), shows how much power you last used.
This was quite fun to make, and I was able to make it look pretty funky using 3D renders and a model I found online (I made the room but found the dart board and darts online). I used a bit of Trig on the darts movement, and made one of my first computer players with this baby.