Here you will find all the basic informations about the game itself. If you're curious how it works, everything is explained here.

Lives:

They tell you how many tries left you have. Whenever you die, you can either give up the run or pay 1 Life to restart from the last checkpoint. Checkpoints are placed at the start of a new area. When you run out of lives, you can only give up the run after dying.
It's important to know that you naturally gain 1 Life after killing any boss. It's important to understand that you don't lose when you have 0 lives. It just means that you can't respawn at all. You can have up to 5 Lives.

Health: 
Health is different from lives. Health is the difference between life and death. You have 100 HP and you regenerate naturally and slowly while you're not shooting. Whenever you hit 0 HP, you instantly die and you are presented with the death screen. 

Shields: 
They protect you from everything that should kill you except directly touching enemies. You start with 0 shield and can have up to 3 at the same time. If you overheat too much your weapon and it gets to a point where it should kill you, then a shield will break instead and restore you to 50% health (if you have any shield charge that is). However they can be broken easily by enemy projectiles (Bullets, Lasers), hazard (Saws, Spikes, Acid), and poison. Whenever a shield breaks, you get launched upwards and are immune for a short time.

Overheat: 
Whenever you shoot your weapon, it gets hotter and hotter. And some point it will start overheating and dealing damage to your character.
It can even kill you if you're low on health. Having a shield prevents death from overheating but breaks the shield. To let the heat go away, simply lay off your trigger-finger.

Movement: 
All characters share the same basic moveset. They can go left, right, jump once, double jump, and comet drop.
Comet drop is activated by pressing the down key while being in air. When you land while comet dropping you create a small explosion impact that damages enemies.

[WORK IN PROGRESS]