Particles

One part i really enjoyed experimenting with was particles since you can do so much with particles, ranging from fire, smoke, rain, dust, waterfall and many more which if you add scripting i think the amount of stuff you can do increases quite a lot such as your character walks on a trigger and steam bursts out of the floor. In my environment i used fire and smoke but i also changed smoke to make steam that flows along the floor giving an eerie effect as the player moves through the level.