FADE is very useful, but you may want to use SPCOLOR and BGCOLOR instead based on what effect you want.
Think of SPCOLOR as changing the color of the "light" that "shines" on the sprite. If you have a pure red surface and shine a pure blue light on it, it absorbs all the light. SPCOLOR is the same way. If a sprite is pure red and you set the SPCOLOR to blue, it's black.
The SB version of Celeste was actually a port done by OBONO, the original was done for PICO-8 and is available online (obviously the developers are the on-screen credits.)
No links because mods
This might be easier:
DEF DIGITS N% OUT A%,B%,C%,D%,E%
VAR S$=FORMAT$("%05D",N%)
A%=VAL(S$[0])
B%=VAL(S$[1])
C%=VAL(S$[2])
D%=VAL(S$[3])
E%=VAL(S$[4])
END
"Don't reupload programs which aren't yours."
I disagree.
If the program isn't available through the creator anymore, first you should contact them to see if they can rehost. From there, I guess rehosting it yourself isn't all bad as long as you provide credit. No reason to let a program go to waste.
If it's still up though, then yeah, don't.