Classic FPS, its a simple shooter, nothing more. The arcade style gameplay is very enjoyable and satisfying, blasting monsters with the shotgun is so much fun. There are many hidden secrets you can find by exploring the map One minor annoyance is NETRISCA. It gives you info on mobs but if you ignore it, it flashes its icon. A thing to note - The game by default is not in widescreen mode. You can follow this article to resolve this : https://www.pcgamingwiki.com/wiki/Serious_Sam:_The_First_Encounter#Widescreen_resolution
This game is very short, you'll finish it in about 4 hours or so. The visuals and atmosphere are amazing and it will look good even on a low end pc. The gameplay is enjoyable and satisfying but the controls are not great especially during the hectic movements. The platforming aspect of the game is decent and the puzzles are easy to solve. But sometimes its hard to discern the background from the main obstacles. The plot is ..interesting, you can get an alternate ending when you play on nightmare mode which unlocks after your first playthrough. Overall, a short, good looking game.