Hey, thanks for the feedback!
The idea was to make it 'endless', but I realize that the enemies are not quite dangerous enough in their current form to make that work. If I improve their attack mechanic to make the game more skill-based the difficulty scaling will be a bit easier to balance.
I like the idea of having a boss with a 1-minute timer :)
Stationary enemies with a buff aura sound interesting too!
I had 3 enemy designs planned, each with their own attack and movement mechanics. They became out of scope as time went by though, sadly.