Lunar Terminator Paradox

There's an optical illusion known by names like the "lunar terminator paradox". This has much discussion and descriptions online, but none made sense in my head, so I wrote this program to figure out what was going on. The paradox: - The moon is illuminated by the sun - After sunset, the sun is below, so we would expect the illuminated portion of the moon to point down, towards where the sun is - ...