Your first task it to light up all the orbs. Do this by standing on all the platforms next to the orbs. Hint: The orbs are the bulb-like things that light up!
Once done, the gate will open and you can move on to the second task, which is hitting 50 targets. TIP: Hold down 'T' on your keyboard for really fast shooting!
Once done, you can pick up your free shield and move on to the third task. You have to complete the maze in order to find the last prize, here are the directions.
Down
Left
Down
Right
Right
Up
If you followed my full guide, you will end up at the last room, where you can get your reward: the suit of Iron Armour! Waddle to the top and pick it up!