A very rough game but with an amazing atmosphere enhanced by the demoscene inspired visuals and the soundtrack by Straylight Productions, the landscapes and the sense of scale this game has offers a very unique experience.

The game is like a mix of Quake and Metroid Prime, there's a lot of exploring ruins, tech bases and alien spaces, reading notes from other survivors and planet inhabitants and environmental storytelling. An interesting direction compared to something more scripted like Half-Life which came out later same year. At its best Unreal lets you explore huge maps, immerse yourself and learn more about the planet you're trapped in.

At its worst you're in hard to navigate spaces fighting very bulletspongy enemies that are hard to hit.
The combat was built around 1vs1 encounters with stronger and "smarter" enemies. The higher tier enemies are very aggressive, they strafe-run, they dodge almost all your projectiles, they can feign death, and they are annoying to fight. The AI may look impressive at first, but it will quickly become apparent that enemies that can just turn invincible for few seconds at random don't make for interesting combat scenarios.
The weapons are fun to use, or would be if the enemies weren't such bullet-spongy slogs to fight with. Seeing what would happen if you made something closer to a deathmatch bot as an AI is a neat experiment but sadly it doesn't really work that well in the end.

Definitely not for everyone, but it's got its own identity and calling it a techdemo is quite unfair.

Portal 2 may be more refined, but it never expanded on what I liked the most about the first game, which was its sense of dread.

At the start, the test chambers have a quite clean, empty, sterile look with a lot of space to move around, but after you escape you'll get to see the inner workings of Aperture, with a lot of claustrophobic spaces, heavy machinery, pistons and other moving objects. The environment becomes extremely hostile, and you get the sense that you're not supposed to be here. This dirty industrial atmosphere is enhanced by the game's soundtrack.

Portal 2 never managed to recapture that feeling, despite a big part of the game being about exploring abandoned parts of the facility. It is a solid game, but it never got me as invested into its world as the first game.