Author: Katutech / Retrowiki Category: Christmas Challenge System: BBC Micro Language: BASIC, BBC Micro Len source code: 74 bytes ptrnbbc.bas Len exe file: 66 bytes $.PATTERN file Len code only: 59 bytes Instructions: Option 1: Copy the following url on a web browser: https://bbcmic.ro/#%7B%22v%22%3A1%2C%22program%22%3A%221X%3D6*RND%283%29-2%3AD%3DSGNRND%3AF.Y%3D1TO19%3AV.31X%2CY%2C42%3AX%3DX%2BD%3AIFY%20MOD3%3D0D%3DD*-1%5Cn2N.%3ARUN%22%7D Option 2: 1.- Open a BBC micro emulator. For example https://virtual.bbcmic.ro/ 2.- Load the SSD disk image ("Games"->"From examples or local"->"Examine" on said web) 3.- Once loaded the disk, load the program by typing: LOAD "PATTERN" 4.- Run it by typing RUN. Description: It chooses a random X from (4,10,16) and a random direction (left or right), draws a zig-zag pattern until Y=19 and starts again. It changes direction each 4 lines. Comments: I'm not sure if the len code is 59, it appears as 59 in the bbcmic.ro editor, see the attached screenshot. Very interesting challenge, thank you.