I killed the puma boss thing without much difficulty on my first attempt today. I’d levelled up a few times first, however, and had picked up some better armour and a couple of cards (which when combined gave me a magic power that made my whip do more damage), all of which helped a lot. I then wandered round for a while trying to find where I needed to go next, which turned out to be pretty obvious as it was somewhere that I needed the “run” power-up I’d just gained from the boss to reach.
Anyway. I then found another boss, died, levelled up some more, and then defeated, giving me another power-up – a double jump! Again, this let me reach places I previously couldn’t, and soon I’d found a third boss, which gave me a sort of dash-attack which breaks blocks – again opening new areas to me.