Some of us remember playing that old confusing 3D game in some gray level where none of the controls made any sense. Chances are that that game was Descent. A game released in 1995 which, despite its many innovation in terms of use of 3D, level design, and AI, was largely forgotten. People say Doom was a proto-Touhou game in first-person, but they've never played Descent. Fly into interplanetary mines, destroy robots, destroy the reactor, and reach the exit before the self-destruct timer counts down.
Descent is a 6DoF shooter, meaning you can freely move in any direction, which the level design makes good use of. Enemies and secrets are placed above you, beneath you, and everywhere around you. Most enemies fire projectile weapons and the level design is rather tight, so you'll have to learn how to dodge. One technique is to hug one side of the wall with the belly of your ship, and then change sides once the enemy fires at you. However, most of your weapons are projectile-based too, meaning you'll have to learn how to lead your shots. Enemies are smart and will often dodge your projectiles. Concussion missiles can destroy enemies with backblast if you hit the wall behind them, but the same goes for you too. Insane is quite insane, but not as sadomasochistic as the Nightmare difficulty in Doom.
Descent 2 adds more new levels, new enemies, new weapons, new missiles, and new gadgets like the afterburner, headlight, and energy -> shield converter which converts surplus energy into shield power, which is quite useful. It also removes the FUCKING CLASS 1 DRILLER but instead replaces it with the fucking Niggerbot in terms of annoyance. You tell me which is better.
Descent 2 is pretty much Descent 1 but better, unfortunately the AdLib soundtrack isn't as big as it was for the first one due soundtrack constraints. Descent 2 also has the Vertigo expansion which adds a whole fuckton of more new levels and enemies, but you'll need to find the files on the internet for it by yourself.
Nobody really talks about Descent 3 outside of the multiplayer.
If you want to play Descent on modern systems, you should first get the games off GOG (magnet:?xt=urn:btih:db24ed5952366034de3db9d6b63d2db43aaa6d82&dn=Descent+%2B+Descent+II+2.1.0.10+%5BGOG%5D&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Fzer0day.ch%3A1337&tr=udp%3A%2F%2Fopen.demonii.com%3A1337&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Fexodus.desync.com%3A6969), and then download the DXX-Rebirth sourceport off: dxx-rebirth.com
The set-up allows you to choose your own soundtrack (some like the redbook soundtrack, some like the classical MIDI versions on this soundcard and so on). You then probably want to mess with the controls a bit, I have sliding up/down bound to Space/CTRL, sliding left/right to W/D, accelerating/reversing to W/S, banking left/right to Q/E, and Pitch U/D inverted (so pointing your mouse downwards also makes your ship look downwards).
Anyways: