For John Bradley, it is xv and xcalc.
For Hisham Muhammad it is htop and LuaRocks.
And for Jason Donenfeld it is wireguard and cgit.
Perhaps some of you have other examples.
The entirety of the works of Fabrice Bellard. QEMU and FFmpeg are the most well-known ones, but there's also a full blown x86 emulator fully and exclusively written in native JavaScript, a greenfield image compression format, a JS engine and probably a dozen other things I only randomly stumble upon and think "oh, wtf, another Fabrice Bellard thing?".
“New Halting Problem solver,” ok, sure buddy, “by Fabrice Bellard”, ok, so tell me how this works…
xwininfo -tree
xdotool windowreparent 0x1e0000b 0x2c0001d