Very rough. For example, first time I fought the mushroom all he did was jump and I mashed X to victory in 15 seconds. Slime can't seem to be damaged, unless he was in an invincible state and I was just supposed to wait. Killer whale was the most enjoyable, attack patterns were well done if a bit repetitive since it takes awhile to chip him down.
Controlling the character isn't bad per se, but it's limiting attacking from the sides and the jump feels a bit choppy. If the character is tweaked to feel nicer to use, I think it will raise up everything else.
Also, nice one with the settings menu.