Hey n8. Some feedback:
Don't use ESC to start. Esc minimizes full-screen mode. Furthermore, using "Normal" menu screens is usually a good idea.
In this kind of game if you have lives, let the player not take damage for a while after taking damage once. Or remove the enemies that are close to the player.
Adding SFXs, particles, and screen shake
Let the player go to the menu screen when they want after they die. WHY DID YOU MAKE IT SO THE PLAYER NEEDS TO WAIT 20 SECONDS!??!?!
Maybe make the enemies spawn on a radius around the player and not in specific locations?
Also, hard mode is too hard. If you, the developer, said you can't beat it, it's too hard.
I won on easy because easy is reasonable:
