Short brainfuck primes

>[-]+>>[-]++>[-]<<<[>[-]+>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-][-]+[>>>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]<<[-]+>[<->[-]]<[<<<->>>[-]]<<<<->>>>>[-]<[-]<<<<<<[>>>>>>>+<+<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]>[-]<[-]<<<<<<[>>>>>>>+<+<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-][-]>[-]>[-]>>[-]<[-]<[>>+<+<-]>>[<<+>>-]>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<<<<<<<<<[>>>>>>>>>>>>+<+<<<<<<<<<<<-]>>>>>>>>>>>>[<<<<<<<<<<<<+>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<[>>>>>>>>>+<+<<<<<<<<-]>>>>>>>>>[<<<<<<<<<+>>>>>>>>>-]<<<<<[-]>>>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<<<[-]+>>>>>[-]]<-<-]>[-]<[-]<<<<<<<<<<<[>>>>>>>>>>>>+<+<<<<<<<<<<<-]>>>>>>>>>>>>[<<<<<<<<<<<<+>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<[>>>>>>>>>+<+<<<<<<<<-]>>>>>>>>>[<<<<<<<<<+>>>>>>>>>-]<<<<[-]+>>[>-<-]>>>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<<->>>>[-]]<[-]<[-]<<<<<<<<<<<<[>>>>>>>>>>>>>+<+<<<<<<<<<<<<-]>>>>>>>>>>>>>[<<<<<<<<<<<<<+>>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<<[>>>>>>>>>>+<+<<<<<<<<<-]>>>>>>>>>>[<<<<<<<<<<+>>>>>>>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-][-]+<[<<<<+>>>>>-<[-]]>[>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]<[<<<[<<<+>>>-]>>>[-]]<-]<<<<[-]+<[>-<[-]]>[<+>-]<[>>[-]<[-]<<<<<<<<<[>>>>>>>>>>+<+<<<<<<<<<-]>>>>>>>>>>[<<<<<<<<<<+>>>>>>>>>>-]<[>>>[-]<[-]<<<<<<<[>>>>>>>>+<+<<<<<<<-]>>>>>>>>[<<<<<<<<+>>>>>>>>-]<<[-]+>[<->[-]]<[<<<<<->>>>>[-]]<<<<<<->>>>>-]>[-]<[-]<<<<<<<<[>>>>>>>>>+<+<<<<<<<<-]>>>>>>>>>[<<<<<<<<<+>>>>>>>>>-]<[<<<<->>>>-]<<<+>>>>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]<<[-]+>[<->[-]]<[<<+>>[-]]<[-]>>[-]<[-]<[>>+<+<-]>>[<<+>>-]>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<<<<<<<<<[>>>>>>>>>>>>+<+<<<<<<<<<<<-]>>>>>>>>>>>>[<<<<<<<<<<<<+>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<[>>>>>>>>>+<+<<<<<<<<-]>>>>>>>>>[<<<<<<<<<+>>>>>>>>>-]<<<<<[-]>>>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<<<[-]+>>>>>[-]]<-<-]>[-]<[-]<<<<<<<<<<<[>>>>>>>>>>>>+<+<<<<<<<<<<<-]>>>>>>>>>>>>[<<<<<<<<<<<<+>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<[>>>>>>>>>+<+<<<<<<<<-]>>>>>>>>>[<<<<<<<<<+>>>>>>>>>-]<<<<[-]+>>[>-<-]>>>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<<->>>>[-]]<[-]<[-]<<<<<<<<<<<<[>>>>>>>>>>>>>+<+<<<<<<<<<<<<-]>>>>>>>>>>>>>[<<<<<<<<<<<<<+>>>>>>>>>>>>>-]>[-]<[-]<<<<<<<<<[>>>>>>>>>>+<+<<<<<<<<<-]>>>>>>>>>>[<<<<<<<<<<+>>>>>>>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-][-]+<[<<<<+>>>>>-<[-]]>[>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]<[<<<[<<<+>>>-]>>>[-]]<-]<<<<[-]+<[>-<[-]]>[<+>-]<]<<<<<[-]+>>>>>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]<[<<<<<[-]>>>>>[-]]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[<<<<<[-]>>>>>[-]]<<<<<<[-]+>>>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]<<[-]+>[<->[-]]<[>>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]<<[-]+>[<->[-]]<[<<<[-]>>>[-]]<[-]]>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<->>[-]]<<]<<->>[-]+<<[<<<->>>>>-<<[-]]>>[<[<<<<->>>>[-]]>-]<[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[>>>[-]++++++++++++++++>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]<<<<[-]>>>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-][-]+<[>-<[-]]>[<+>-]<[>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[<<->>-]<<<<<+>>>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-][-]+<[>-<[-]]>[<+>-]<]<<<[-]>>[<<+>>-]<[-]++++++++++++++++++++++++++++++++++++++++++++++++>[-]+++++++++>>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<+++++++>>>[-]]<[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[<+>-]<.[-]++++++++++++++++++++++++++++++++++++++++++++++++>[-]+++++++++>>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<+++++++>>>[-]]<[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<[<+>-]<.[-]++++++++++++++++>>[-]<[-]<<<<<<[>>>>>>>+<+<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]<<<<[-]>>>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-][-]+<[>-<[-]]>[<+>-]<[>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[<<->>-]<<<<<+>>>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-][-]+<[>-<[-]]>[<+>-]<]<<<[-]>>[<<+>>-]<[-]++++++++++++++++++++++++++++++++++++++++++++++++>[-]+++++++++>>>[-]<[-]<<<<<[>>>>>>+<+<<<<<-]>>>>>>[<<<<<<+>>>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<+++++++>>>[-]]<[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<[<+>-]<.[-]++++++++++++++++++++++++++++++++++++++++++++++++>[-]+++++++++>>>[-]<[-]<<<<[>>>>>+<+<<<<-]>>>>>[<<<<<+>>>>>-]>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<<[-]>[>>>>[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<<[-]+>[<->[-]]<[<<<[-]+>>>[-]]<-<-]>[-]<[-]<[>>+<+<-]>>[<<+>>-]<[<<<+++++++>>>[-]]<[-]<[-]<<[>>>+<+<<-]>>>[<<<+>>>-]<[<+>-]<.<<[-]++++++++++.<[-]]<<+>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<[-]+>[<->[-]]<[<+>[-]]<<<<[-]+>>>>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<[-]+>[<->[-]]<[>>>[-]<[-]<<<[>>>>+<+<<<-]>>>>[<<<<+>>>>-]<<[-]+>[<->[-]]<[<<<<<[-]>>>>>[-]]<[-]]<<<<]

Try it online.

Mandelbrot set sketch in Scratch

Despite my personal disbelieve in and dislike of the colored blocks dragging simulator 3, I nevertheless wanted to extract functionality other than the hardcoded cat mascot path tracing from the aforementioned software; one of the most efficient visual result to build effort ratio yields a simple plot of the Mandelbrot set, formally known as

M:=\{z\in\mathbb{C}:|\lim_{n\to\infty}\mathrm{itr}^n(z)|<\infty\}

where the iterator is defined as

\mathrm{itr}^n(z) := \mathrm{itr}^{n-1}(z)^2+z, \\ \mathrm{itr}^0(z) := 0.

The render resolution is kept at a recognizable minimum as not to overburden the machine tasked with creating it. Source: mandelbrot-set.sb3

A Scratch render of the Mandelbrot set.

Mostly Misaligned Mirrors

Recently my stochastic professor introduced me to a problem he has been pondering for over two decades: on the two-dimensional integer lattice \mathbb{Z}^2 one shall flip a three-sided coin for each point and uniformly place one of three mirrors, \{\diagup,\,\cdot\,,\diagdown\}, where \,\cdot\, denotes not placing a mirror. After having populated the world, one picks their favorite integer tuple and points a beam of light in one of the four cardinal directions. With what probability does the light fall into a loop, never fully escaping?

Simulating a beam of light bouncing off mirrors.
A cycle which includes the origin.

Continue reading