Here I am going to explain everything about the mechanics of the game.
It's gonna be more of a list of useful stuff to know about if you want to understand the gameplay better.

Q: The tutorial said something about shooting at my feet?
A: Your weapon has knockback. It pushes you in the opposite direction everytime you press the trigger. This allows you to make longer jumps or to fall down faster.

Q: What are candy-ups?
A: They drop from enemies, portals, and some props. They vary from common to legendary. Just eat them and you'll see.

Q: What is overheat?
A: Everytime you shoot your weapon warms up. If you overheat, you hurt yourself while shooting. Regenerate by letting go of the trigger for some time. Overheating can kill you so be careful.

Q: What do shields do?
A: They protect you from everything that can hurt you but that is not an enemy. So we're talking about spikes, saws, acid pools, hostile projectiles and even your own weapon's overheat. 

Q: What is stomp exactly?
A: Ok, so by default you can bounce on everyone's head. Flying enemies will take damage from that. Stomp is a passive trait that can be either disabled or enabled. When enabled bouncing on any enemy will deal your weapon damage to them.

Q: How do I get stomp then?
A: By lucking out the stomp candy-up (which is epic). The stomper has stomp enabled by default (who would've guessed).

Q: Why do Bosses drop a legendary candy-up if I can't even enjoy it before the level ends?
A: Mmm if only there was a way to make those useful...

Q: What are those big ugly portals that pop up from time to time instead of regular portals?
A: Breaches. They are the better version of the regular portal. 

Q: I dont really get how shrines work.
A: Think of it like an oven. Enemies are the fire and the delicious bread it gives you is a candy-up. Each enemies killed near a shrine upgrade the candy-up it holds. When satisfied with it, just pick it up from the shrine. The shrine is disabled for some time after being used.