Breathing LED controlled by temperature sensor (NEED HELP!!)

[system]

There are 5 speeds (as derived from the map scheme), or levels, or whatever you want to call them.
So, when it changes a level, from 3 to 4 or 3 to 5 (for example), it can/will, by the looks of it here, cut short instead of winding down, no matter where it is in the curve - bang, it starts anew.

The transition to a new "speed" shouldn't be allowed till the output is at "0".

I understand you, the wave should only change if the output is zero, but how do I write the code? Thanks