double jumping quite silly. hitting the jump button for 1 frame after jumping (the window to do the actual input is pretty gigantic, but somewhere around when you reach the peak of your jump/start descending, US version allows you to triple jump, the japanese version lets you go beyond.
Here's a more accurate explanation:
They wanted to implement variable jump height so that the longer you hold the jump button, the higher you jump. Their solution was that once you're in the air, you're given 2 frames (5 in japanese version) in which when you hit the jump button, you'll jump again. What this usually means is that when you jump from the ground and you hold the jump button, you're really jumping 3 (or 6) times.
They screwed this up though, and they don't check to make sure that all these jump frames are back-to-back. This is really obvious when you walk off of a ledge and are able to jump afterwards.
The most reliable way to double jump is to tap the first jump for 1 or 2 frames. The 2nd jump you can just press normally. Not sure how everyone else does this, but I use my thumb and snap the button. I wear a crappy winter glove I bought from the grocery store for $3 to reduce the pain because it hurts after a while.
Wow thanks!!! That was mega helpful. I really do appreciate the accuracy of your description. I'll try it out and let you know how it goes.
Thanks again!