Charlie Ninja/Fridge

Fridge Logic

 * Sometimes spikes are hidden into boxes and barrels instead of bonuses: if you step on them, you will lose energy, but then enemies who step on them also get hurt, stopping for a while and rendering them easier to kill. However, spikes are the only trap in the game that can hurt them... they are immune to everything included flamethrowers and land mines (the player, obviously, is not)!