Pretty cool demo with some nice sprites and effects, not surprised to see solid shmup mechanics since you already showed some in the past :)
Also having a cactus be a wizzard is certainly something you don't see everyday :p
There's no lives in this demo but i feel the screen gets "bullet hell - ish" a bit too soon and makes the game quite hard but nothing a bit of balancing can't fix.
I like that you get a circular spam fire of your own to use though ! And the full menu with control layouts for both keyboard/controller and the bg color change and all are nice.
So appart from the difficulty balance, i can oly agree with what's been said already, add in win/lose conditions, a score and you got yourself a cool game, which if you make it endless score base can be pretty well suited for mobile as well.
Good job there dude ^^