Next time when you design a game similar to this one focus on;
Enemy Wave Spawn - Avoid spawning too many enemies because the game began to glitch and slow down.
Use of screen space - Around 80% of the screen is blank and not used. In the case of your game design you could zoom in onto the player a bit more (having around 50% or less of the screen dark).
Level Design - Make the level layout smaller in size to have the player not feel they are running in the middle of nowhere forever.
Overall, not a bad use of fog of war element along with the pick and drop mechanics of items.