It's a 3D puzzle game and not a very good one. The story and world building can only by described as "SuperCringe", even though I hate that particular word passionately. Shit-tier memes. Another popular game that didn't live up to its name.
I'd swear it used to be better. Stages #2 and #5 (top-down view) are crap. Cutting them out would make Contra III a much more enjoyable game. Still decent.