Nice game ! Very polished for a 3 hours submission :)
Especially, you thought to add instructions, virtual controls, several difficulties... These are things I tend to forget even for bigger jams, so for a 3 hours one, it's very nice to see these elements included !
Double jump is indeed tricky, especially to reach the maximum height, but otherwise controls feel very good.
I only tried Medium difficulty, up to level 6, and enemy patterns felt well balanced.
I started having trouble at level 5 when double jump became necessary to avoid both rhino and bird at the same time (not especially due to the controls, though. My brain was actually wanting to do a "small" jump between both enemies instead, by pressing Space quickly)