Where to start...
You cant see the Projectiles
The Enemies shoot out of screen
You can't see what will damage you and what not
Things that will damage you are hardly visible
You don't have invinsible-frames when you get damage, so you will lose all your lifes if you jump in an enemy
There are a tons of blind-jumps in the game, that will kill you
Enemies are hidden and its often not possible to go back, so you often have to restart, because you didn't see an enemy
The map has many parts where the enemies can hit you but it's impossible for you to hit them and you have no way to dodge them because you're standing near a cliff
And even if you still made it trough everything, if you died, you have to do kill 20min. long all 40 enemies again
AND even then if you played trough all this, then the game will break, if you die in the last level