Here in the menu you can pick your difficulty and your stage if you have played some of the levels already. I had played up to Level 6 on Normal difficulty so that's why you see the 6 there. But now it's time for expert! The main difference between the difficulties is actually how fast you go. On normal, you go a decent speed. On expert, you zoom by so fast everything becomes a blur.
Racing into action! I'm one of the white ships, fighting against a bunch of other white ships and avoiding pink projectiles. The controls are super simple. Move with the arrow keys, press Z or hold Z to fire, and press Alt to charge up a shot. You can go reaaally fast (especially uncontrollably fast in expert) but I find that pretty fun!
On top it shows how much time you have left until game over. Bottom right shows how fast you're going, though it's really hard to pay attention to the HUD when you're going fast and avoiding all the projectiles.
If you see at the end of my firing, there's some star like projectile. That is the charged shot. It can even go through enemy projectiles! Only problem is it slows you down while you are charging for it.
The levels differ mainly in color. Although what I was seeing at that point was a blur of colors while I was spinning around.
It's kind of those yellow things to be at the sides. I'd have fallen off multiple times otherwise! Oh, each hit you take takes off 15 seconds from the timer. So you don't want to take too many hits! You don't have lives or anything, just lowered time.
And when you run out of time, game over!