Somewhat related: turing complete (Open)TTD.
segment display: https://www.tt-forums.net/viewtopic.php?f=29&t=37902 (2008)
digital clock: https://www.youtube.com/watch?v=mkQBGJeh12U (2011)
binary adder: https://www.youtube.com/watch?v=fwWo9fL-GZs and https://www.youtube.com/watch?v=YyEzm1ghAsU (2015)