The music kicking in for Monkey Mode was great! It helped keep me going until level 19 where I got stuck only ever being able to collect 9/10 bananas before being crushed between the walls of gorillas.
The gameplay is fun, but I did become fairly frustrated by the sliding gorillas who follow the player's movements. It felt like the timing to get past them was a bit too precise, especially when I kept hitting the sides of the walls while going past which would slow me down and cause me to be hit.
It's a very well-polished entry though! The amount of variety that was added from the simple base gave it solid depth throughout.