SHOOTIFENCE

It looks like a shooting game, but it's essentially a tower defense game.
You continuously defeat various types of enemies that appear from above without missing any, while infinitely growing three types of weapons with different characteristics.
The three weapon types are: the Vulcan, which has rapid fire and many bullets; the Laser, which has penetrating power but no rapid fire; and the Missile, which explodes on impact and deals damage to surrounding enemies.
Each can be equipped separately on the left and right sides of your ship and grown independently.
There is compatibility between enemies and weapons, so depending on which enemies appear, your currently selected weapons may be more or less effective against them compared to other enemies.
The enemy placements, weapon change options that appear, weapon growth options, and so on are fixed each month. The patterns change when the month changes.

Most likely, in the end, the enemies themselves won't be your greatest challenge—it will be the existence of the weapon change options. . .