I understand “fluid” is a bit ambiguous. I’ll try to be more specific. The opinions I write are merely my own, and the way I feel when playing. It does not mean what I say is correct by any means, so please take it with a grain of salt.

1. The response it takes for the player to move when we click the arrows is a bit slow. It takes some time before the player get to full speed. Some more acceleration would help.
2. The player glides a little too much for my taste when I want to suddenly move the opposite way. This is especially true when the player is mid-air.
3. I thought I could climb the ladder if I kept holding the up arrow, but it didn’t work when I was moving forward at the same time (I had to release the left/right arrow to be able to climb the ladder.) I think this was the reason I wasn’t able to get the jumps right.