About sixty seconds in, my inner ear filed a formal complaint. Flying with no up and no down is definately a skill and I do not have it, so my entire go was spent upside down against a wall while things shot at me. That is more my problem than the game's, to be fair. Still can't put my name to something I couldn't stay level in.
The N64 six-degree shooters were a small genre of their own and then they basically evaporated, so finding one sat in a browser window is a small joy. Arenas are tight. Pickups earn the trip across the room. Orientation is the real skill test. That shape holds up and nobody needed to modernise it much.
6DoF done properly is rare and this one understands the brief. You get full freedom, there's no ground plane to cheat against, and the aim punishes you for not tracking in three axes. Levels built in Hammer, and that's why the the arenas loop cleanly and read as places rather than boxes. Quick under the hands. If you know what Forsaken was, you already know.
Six degrees of freedom done properly, in the Forsaken tradition, which almost nobody attempts any more. Levels built in Hammer and it shows: real architecture rather than a box with things in it.
