This is a game I actually played when I was much younger. I was looking through some abandonware site, and my little 8 year old self (or however old I was at the time) glew up in excitement seeing a game that looked as beautiful, explosive, & violent as this one.
I ended up loving it even more than I thought I would, and it became something of just a fond memory of mine once my dad got rid of that PC.
Now, after finally realizing the name of the game, I found this and I am beyond happy to see that GOG is supporting it!
As for the game itself (because that's what you're really here for, right?) It's still an absolute blast to play and it has aged tremendously well; much more than other platformers of the time. The platforming is satisfying, the graphics are very smooth, animations are fluid, weapons are awesome, the atmosphere kicks ass, there is plenty of enemies and things to keep the game from feeling stale,, the game is tough as balls at times but while still feeling fair, just, literally EVERYTHING with this game is done right, and I'm not speaking that way purely out of nostalgia. I think it is still a legitimately good game.
I was very close to knocking off one star. Obviously, I decided to keep it upon getting this far. But why would I do that for a perfect game like this? Well, there's no music! NONE at all. No ambient stuff, no metal stuff (which would be really fitting for this), no anything. Luckily: 1. The sound design is still great on its own so you probably won't get bored without the music, and 2. This means you could play whatever the hell you want in the background without it feeling like you're taking anything away from the core experience.
I recommend playing The Return by Bathory (especially), anything by Slayer, Scream Blood Gore/Leprosy by Death, or really any kind of metal album that's fast or aggressive.
Do yourself a favor and just grab this game. If you like platformers at ALL, then you will surely not be disappointed with this one.