I add some sizing problems on the embeded version, maybe you can solve this using better minimal webgl template, who has a fixed reference size option, or using the itch.io fullscreen option.
It was really difficult for firsts times (hardly beat 40 BPM) because I was alternating betwin protection, heal and addapted atttacks. After I read the comment about alternate heal and wind attack, and I reach easily 90BPM. Maybe you can make the "cooldown" (use the same power nerf it) stronger, and set full power spell stronger too (like for heal : heal you at full life, but take 3 turns to get back to this full heal (or somewhat like this (you get the idea)))