Serious Sam Classic: The First Encounter

The beginning of pure chaos. Endless waves of enemies, huge arenas, and that unforgettable first scream of a kamikaze running at you.
It’s simple, dumb, and insanely fun. A true FPS classic.

Certainly a serious game with very serious enemies and serious bossfights

Probably the best Serious Sam game. Lots of big fights, trapped ammo/health pickups, and silliness. You need to quicksave often because the game isn't remotely fair. The first few levels are a bit slow and annoying because you don't have all the weapons yet.
Unless you're playing on tourist/easy, the gameplay isn't just dumb shooting. You have to prioritize enemies and switch weapons constantly, otherwise you will get overwhelmed. It is a unique type of gameplay.
Compared to the "Classics: Revolution" version: this one works better.
Compared to the HD version (or Fusion), this original version has a few gravity gimmick rooms that weren't ported over. It doesn't matter much.
Compared to The Second Encounter, this has fewer enemy types and weapons, and only one setting (Egypt), but more big difficult fights.
Compared to SS2, this is much less goofy.
Compared to SS3 and later, this has no NPCs talking in your ear, no running, ~no reloading, no aim-down-sights.

A very serious game about a very serious man on a very serious mission to save the world! On a more serious note, it's quite impressive considering how small the team who made it is. In some ways it does feel like Doom, however, the maps are ginormous. And something I really appreciate is that there weren't any invisible walls. If you can reach it you can generally go there, on the few occasions when the map is outdoors and open, there was a "sunburn" mechanic slowly ticking at your health to prevent wandering to far off, but all the other constraints were natural walls and hills. I actually managed to jump on top of a wall with rocket jumping in some levels and either use it to my advantage in overwhelming fights or explore out of bounds. And I'm pretty sure it's intentional, since in the final level they've integrated a gentle "force" that prevents you from jumping on top of a wall, hence they've know it's doable. Explorations was also fun and there were a handful of secrets that were more for giggles on the devs' side and add a more personal touch to the whole experience.

pretty neat game, not too difficult, kinda reminds me of a mix between doom and wolfenstein
if you enjoy fps games, especially good retro shooters, pick this game up for your collection.

When you play on Linux, you can use a Steam Play option called Luxtorpedia which will automagically run your installed files through a native source port of this game and other supported titles!

Pretty fun, enough so to recommend. The guns all feel pretty powerful save for the pistols, and it ends on a pretty high note. With that said, some of the enemies in this are not difficult but quite annoying to deal with over and over again. It's not so much a challenge as it is a routine of learning when and where the suicide bombers or skeletons or alien bulls will spawn so you know to switch to the right weapons. It's at least a little funny that the very first game earned the entire series' reputation for running backwards while shooting hordes and hordes of enemies from the get-go but god does it drag at times.