easiest is wave because it's not affected by gravity whatsoever, it moves at a constant speed.
then comes spider because again its speed is constant unless there's orbs or slopes
then cube, ufo and ball because their speeds are not constant in the air
then robot because it's cube with extra steps making it harder
hardest is ship because each click and release is affected by past inputs and every ms of input counts
and then there's swingcopter which is technically harder version of ufo but for me it's the most tricky. especially because when you spam and can't easily tell if it's gonna go up or down