Fillin

Fillin (pronounced \ɸiɭiɳ\) is an esolang created by User:Yayimhere after being dissatisfied by Square-like, another esolang they made. Fillin functions by filling in its own program again and again. Fillin uses a pointer initially going right.

Memory

Fillin has a stack. This stack is filled with bits. Every command's bit sequence is pushed.

Commands

Fillin has the following commands, each a "line" of two bits:

• 11 enter the program
• 10 leave program, and jump to the new "enter program" command(see leave section)
• 01 rotate 90 degrees clockwise
• 00 NOP

always choosing the leftmost and uppermost 11 to enter with.

Leave

When a program leaves, we start with filling every bit in the program with (for only symbolic reasons) #'s. Then for every # starting at the upper left most # and ending in the rightmost bottommost #, we pop a bit, and replace the # with that bit, until every # has been filled in. Do note that this filled in version doesn't replace the program, but is copied to empty space around the original program, specifically a Moore neighborhood.