Fun little game! I didn't realize at first that you needed to do the chargeup and press space when you got to each girl to complete that one at first, but it did make a good excuse to see the fail ending.
Yeah, that's fair. I think a little text popup kinda like how WarioWare microgames work would be helpful. Like "Press Space!", "Hold Space" and "Hold Space, then Press!" could work. Or, just make it clear in the dialogue that the final one is a combination of the other two. Something like "This one will put all my skills to the test!"
But I don't think it even necessarily needs to change, either. It's short enough that it doesn't really matter.