Pressing keys is the main thing. The game has a health bar at the bottom that turns red if you miss notes, which is a key mechanic. You must hit the arrow when it intersects with the target arrow to keep your health up.
Playing on desktop requires pressing Enter to start, which is kinda weird anyway. The arrow buttons need to be pressed when the arrows intersect. Their is a pause function using Enter during the match. The health bar shows green parts that deplete if you fail.
Quick tip i found is to watch the health bar closely. When the green part disappears completely, you lose the round, so it is better then just guessing. The mobile version splits the screen into touch areas, and you tap the area matching the arrow color when they intersect.
Gameplay stuff involves pressing buttons when arrows match up. The health bar thingy at the bottom is crucial, as the green part fading means you are losing. On mobile, the screen is divided into colored touch zones, and you tap the right one when the arrows cross. The arrow intersection mechanic is the core feature.