Playing FLAT
Your ultimate objective in FLAT is to defeat the Pulse Dragon.
Find additional weapons and healthkits by collecting Supply Capsules. Supply Capsules can be identified from a distance by a downward pointing "skybeam".
Enemy skaters will hunt you down, so be sure to finish them off.
General playing tips:
-----
Hold down the W key to skate faster.
Combat music cues can give you advanced warning of enemies approaching from behind
Keep an eye out for skybeams to your left and right
Jumping can be used to dodge projectiles and hop over small crystals
Combat is easier when skating backwards

There are also a number of gameplay settings that can be adjusted to tune the game's experience to your preferences.