LAG? Try it at https://turbowarp.org/925605310/ Enter the pyramid and try to find the Pharaoh's tomb! (There are two different ways to get there. There is no specific ending once you've found it.) Arrow keys / WASD to move. Click on shapes with glowing yellow outlines. Be observant. If you can't solve a puzzle, look around a bit more.
This has taken too long; the code has become messy; and there is no specific ending. But I'm out of energy. It uses a few techniques I haven't tried before, including the drawing of the floor, which I might demo separately at some stage. Thanks to @DadofMrLog for the triangle-filler.
