Write a note: double-click any empty spot on the wallpaper and start typing. Click anywhere else when you're done. The text stays on the desktop with no box or border, behind your windows like desktop icons.
Edit a note: click it to put the cursor back in. Enter starts a new line, Esc finishes editing.
Copy text: drag across the text to select it, then press Ctrl+C. Double-click a word to select it, Ctrl+A selects everything. With nothing selected, Ctrl+C copies the whole note.
Move a note: drag the small gray square beside its first line (it shows when you point at the note), or hold Alt and drag anywhere on it.
Right-click a note to copy, paste, change its color (black is the default) or delete it.

A note you empty out disappears on its own. Notes save automatically to %LOCALAPPDATA%\QuickNote\notes.txt and come back after a restart.

The tray menu has New note, Hide all notes, Start with Windows and a help screen.

Notes

The exe is unsigned, so Windows SmartScreen may warn the first time. Choose "More info" and then "Run anyway."

Building

Plain Win32 C, no dependencies beyond the standard Windows DLLs.

sh build.sh

Requires MinGW-w64 (x86_64-w64-mingw32-gcc and windres).