10

10 has two valid chars, 1 and 0, whitespace like newline, space, and tab are also valid, all other chars are comments

Syntax of program

[x]+ in syntax is x happens 1 or more times
[anything] in syntax means any of the other syntax things
[x]? in syntax is x happens 0 or 1 times
{x:y} in syntax puts y in x
10 starts the program
01 ends the program
11 {name:[101]+} starts a function with name
00 ends a function
000 nop
001 {var:[111]+} {val:[anything]} sets var to val
010 {var:[111]+} refers to var as var
011 {name:[101]+} runs name as function
100 {val:[anything]} returns val
101 {val:[anything]} outputs val
110 {prompt:[anything]?} gets input with maybe prompt
111 {val:[010]+} is a value
0 {val:[anything]} 1 brackets around val

3 program

10 start
001 111 0 111 010 010 010 1 set oneoneone to tree
101 010 111 output oneoneone
01 end