Techniques: Boost Jump
The Boost Jump is a technique that uses the Boost Ball as a substitute for Morph Ball Bombs when climbing up walls.
To perform a Boost Jump, first charge up the Boost Ball, then roll into the wall you want to climb. About three frames after the Morph Ball collides with the wall, release the Boost. If you are lucky, the Morph Ball will shoot up into the air.
You can also Boost into the wall, then Boost again about three frames after the Morph Ball collides with the wall. Boosting initially instead of just rolling into the wall may increase the chances of the Morph Ball bouncing correctly.
The technique works because sometimes the Morph Ball will bounce straight up a wall when rolling or Boosting into it. Once the Morph Ball is pointed up and moving up the wall (even very slowly), Boosting will provide the rest of the necessary acceleration in the same direction.
Getting the Morph Ball to bounce straight up when colliding with the wall is the hardest part of performing a Boost Jump. There doesn't seem to be a consistent way to achieve the correct bounce. Sometimes, the Morph Ball will bounce left or right instead of up. Sometimes, it will do nothing at all.
In some rooms, the Morph Ball will climb up the wall on its own, without having to roll or Boost into it. This phenomenon makes Boost Jumping much easier, because the game just gives you the hardest part of the technique for free. To check whether the Morph Ball will climb up on its own, first roll into the wall you want to check. Then slowly roll the Analog Stick around in the same general direction as the wall. In other words, you want to press into the wall with the ball while slightly changing the angle of the stick. Stop moving the stick and hold it still if you see the ball start to jump up on its own. You may also see an animation with little sparks flying out. If you keep holding the stick, the ball should keep jumping up and down on the wall, trying to climb it. When you sense that the ball is about to jump up again, release your Boost. Again, the timing (only about three frames) is too fast for you to react to the ball starting to climb, so you have to anticipate when to release your Boost. Unfortunately, this special setup doesn't seem to work on most of the walls in the game.
Examples of Boost Jumping include escaping Burn Dome without using Morph Ball Bombs and escaping the room below Warrior Shrine without using Morph Ball Bombs.