I got up to 47 and just got fed up with how unresponsive the controls are. At that point I was just inching through to see the next portion of each level because every obstacle was requiring me to press the buttons before I knew where the character would end up. On top of that, half the runs would end with one of the buttons just not working.
A couple bits in particular that annoyed me:
-- The levels should fully restart after a death. That way the player can immediately start again with the knowledge that things will turn out the same for the parts they've already succeeded at.
-- The actual number of dashes and jump the character is allowed to do is really unclear, since there's no good time to see what does and doesn't reset the count.
-- The cannons shooting while outside the screen and generally without any indication of timing causes a lot of that section be pure luck.
-- The fireball mechanic being introduced in the middle of the level basically guarantees the player will have to do the first part at least once more no matter how good they are.
-- The level with the upward cannon that shoots slow balls takes a really long time to start.