Puzzles - it's all just peaceful puzzles, like overly elaborate contraptions to open doors or unlock new areas. There are no enemies or time pressure. When it was released, there was no way to look stuff up to solve them, so it was really captivating.
Try really hard not to google the solutions, since solving them by yourself is really satisfying.

Edit: Can't really think of a modern equivalent, or I would buy it. If you "rage quit", there's something wrong with you - it's way too mellow for that. You might want to take a break and come back, but you're not gonna be hurling controllers.

And it's kind of pseudo 3D - like from each position, you can click forward, and look around from a new vantage point, but you don't seamlessly navigate a 3d space like a modern game.