Incubus Pulsum Walkthrough
You won't win on your first try, but don't give up! The game seems easier and easier every time you play through it. Eventually you'll be 5-clouding hard mode every time you play. Not insane mode though, it's nearly impossible (but don't worry, there's nothing it unlocks anyway)
If a pattern is side-diagonal-side, hold the side button down through the whole pattern and just tap up or down when the diagonal one comes through. Same way for up-diagonal-up or similar patterns.
The hardest key combination is up and down at the same time. Make it easy for yourself and use 1 finger to hold down both keys.
If you're having trouble hitting notes on beat, try to concentrate more on the music than the visual representation. This will help, but it doesn't mean you can close your eyes and play.