Expert

Now we finally reached the point of no return. Those techniques will progressively become harder and abuse on certain game mechanics. Which means that those techs aren't hard coded.

Tech:

The Ultra Dash:

The concept behind this one is simple. It is a wave dash interrupted by a down diagonal dash (you know if you input it correctly if there isn't the speed rings from those previous techniques). After that just jump on a platform after a few frames and you are golden. In Celeste there is no real speed cap, so if you manage to always find a platform to jump on then dash diagonally down again and vice versa you can technically gain near infinite amount of speed. There is two problem though. The first one is that it is extremely unlikely you find more than 2 blocks space out in such a manner. And second it is very hard to control yourself with this much speed. Other maps will more likely use other way of multiplying Madeline's speed. Like moving blocks or other interactable.

The Corner Boost:

Yet another way to increase Madeline speed. Just input a climb jump instantly with very high speed at the edge of a platform. To gain more speed, you can either be moving very fast from the start or just input a horizontal dash at the right timing. (as shown in the example) 

The Corner Jump: 

Yet another tech that requires a corner. Normally in Celeste spikes, hurts you. But if you happen to be at the corner of a platform filled with them. You can buffer a jump to safety. (Buffering something is basically input your action in advance. So that whenever your character is ready to perform the action it will perfrom it imidiately. This game mehcanic is present in almost every platformer including Celeste).