OMG why didn’t you post this earlier? That’s an excellent solution. It indeed had nothing to do with geometry and the red triangle was there only for padding since binary ASCII has to be divisible by 8.
So the binary you get from the image is
00000010 00100000 00100010 01110100 01100110 01100101 01111000 01101001
01110010 01101011 01101100 01100011 01110010 01101011 01111010 01100110
01100101 01101010 01110000 01100110 01101100 01101110 01100110 01100101
01101011 01111001 01110110 01000111 01011010 01010001 01010001 01010010
00100010 00100000 00010111 00000011
The first and the last 2 characters are actually ASCII control characters meaning “start of text”, “end of transmission block” and “end of text” respectively.
If you convert the binary to ASCII, you indeed get
tfexirklcrkzfejpflnfekyvGZQQR
The only remaining thing is to rotate the alphabet by 9 letters to the right and the text changes to
congratulationsyouwonthePIZZA
So congratulations, you (almost) won the pizza.