By all means, a solid idea. Here are just a few suggestions, some of which I saw in the comments below already: don't let enemies spawn so close to the player either by adding a radius to block spawns or making it happen off screen, color the projectiles and the enemies using colors that stand out from the environment as its easy to just get visually confused, maybe add random objectives throughout, like destroy an object that spawns every so often to the player has a reason to leave the safer edges of the map.