Really good first (first.5?) game! I like the graphics, and the simple animations are great.
What to work on:
Game feels really empty, especially for the first bit while enemies are still spawning in, I'm assuming (I could be wrong) they spawn in from the edges of the map, so it takes them a decent while to reach the player. In the future I'd made a spawn point and keep it just out of the player's view so enemies spawn closer to the player.
More decor in the map would be nice too, give a bit of variety to the map and make it more challenging to avoid enemies, currently it's very easy to get enemies to line up and shoot them all down.
Overall! Great first go! I can't wait to see what you do next! :D