Made a little bit of progress today.

• Enemies spawns on the sides and have 3 different shooting patterns (5 bolts, 3 quick ones, 5 on a semicircle)
• Player can shoot down enemies.
• Player can lose and after that an upgrades menu is shown

Also I'm starting to make some drafts for the castle and spaceship (player), they look quite simple but with some animations and camera shakes should be good enough. Later I'll keep working on the art side.