One of the standout things about this game is the variance in the levels and boss fights. Just when you think you've got it all figured out, the game throws you a curveball and you're like "whoa, didn't see that coming!". It's these weird surprises that make the game so memorable and keep you coming back for more.
The challenge is another key aspect of the game. As you progress through the levels, it gets increasingly difficult, and you'll need to be on your toes to survive. But it's not just about difficulty - the game also has a great sense of flow and exploration, which makes it really hard to put down.
How to play the Touhou PC-98 games in your browser! (Touhou 1-5) - YouTube