This was a fun retro shooter! Loved the EGA-style graphics, all the creature designs and environment art. I think it could be improved some, for starters it isn't very difficult. There were a lot of health pickups, most I did not need.
The issue is the AI. You have a lot of enemy variants, but beyond some having more damage than others, they're basically all the same -- beyond a couple that had projectiles, and 1 that was a stationary turret. I found them just too timid, making it easy to kill them. You need to make some more aggressive, like the tank ones. Others you need to make faster. Maybe consider adding monster closets -- if the engine will support it. The only real challenge was the final boss, but only because it had so much health and had 3 stages. Bit torn on the boss, as I personally don't like boss fights that drag on, but I think it would be fine to leave as is as long as you make the rest of the game more of a challenge.
I also think that perhaps more weapons and pickups with various effects would be nice. Regardless I would first focus on the enemy AI design, and maybe add in a projectile effect for the player weapon as a bit more polish -- make it really feel like you are shooting energy bolts from your staff.
Overall this was a fun experience for someone who grew up playing these old shooters.