I like the idea of a "clicker" style game being done like this; The sprite work for the enemies are really well done I like the style and the shading on them. The music is a bit loud at start but nothing adjusting on my end did not fix, it sounded alright.
I would suggest changing the layout of the UI so you can see more directly which character the health bar relates too as at first it is confusing as the bars are the exact same and their placement does not tell the user much. Over all nice game.