we had this project in uni to make a windows forms c# app for a fixed predetermined premise (in my case it was some advertising accounting thing)
since the premise was rather simple and we weren't given much wiggle room i decided to get more creative with it by making its style somewhat based on old amiga software, specifically music trackers (sadly there are no neon equalizers this time)
it uses datagridview and can read and write from txt files, calculate profits and and return subtotals among products, groups or channels
it's kinda useless (basically a less functional sql db) but it was fun to do at least
another one (simple minesweeper)
at first i planned on using fast fourier transform convolutions again for finding cell neighbour counts but decided against it because it would only complicate things more
maybe i'll do it in the future... implemented through some sort of internal bitmap wizardry (would make flood fills for uncovered zeroes easier too probably)