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Hi Sean, Sorry for the late response!  I will check notification settings.

By alpha I mean like a graphic alpha channel (transparency). In Pico-8 black is transparent. 

In my case, I'm making a particle explosion and using shift-e and shift-b in the function FILLP(E) or FILLP(B) (where it shows the dotted pattern in place of E and B, with the built in patterns; which use color 0 as an alpha, and my chosen color as the fill pattern.  

In your red/yellow example above, if the Red was color 0 (black), it would be transparent and you would only see yellow diagonal lines. Any circle filled with that pattern would show the yellow lines and what isn't yellow would show the game graphics under the fill where the color 0 is.  

I'm new to programming but I did a lot of graphic work, so I might not be explaining it well. I thought this would help me fade out a filled circle by changing through a series of patterns with less and less coverage.  That's what I'm doing now with the Shift-E and Shift-B, but I only get 2 steps of fade where I'd like about 5 or 7.

Again, I love this tool, I can't thank you enough for your contributions to the community!!! I appreciate it!

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Ah, I think I understand what you're trying to do.

"Transparent" isn't a colour to select in PICO-8 (it defaults to treating black as transparent, but you can modify that with PALT), and the FILLP function allows you to set part of the pattern to transparent (regardless of colour) using additional binary bits. Using the previous example, you could call FILLP(0x8421 + 0b.1) and it will render transparent where the yellow is. There's more detail on this feature in the PICO-8 user manual here.

I assume when you're using the special characters shift-e and shift-b, it's using a pattern that already has that bit set, but if you want to use custom patterns you can add 0b.1 to any pattern you create.


Thank you so much for that tip!  I'll certainly dig into the manual and add this to my own quick notes.  I will put this to use!!!


I just tried this out, and it's exactly what I needed to make a smooth fade (given the color and resolutions limitations, haha)  This is perfect!