the instructions are written on the first slide, but in case you didn't read them, I've written them here- 1) right arrow key to see the purple gem. 2) left arrow key to see the blue diamond. 3) press both, right and left, ( not necessarily at the same time) to see both. 4) move your mouse pointer, to make the gems move. 5) press the spacebar to see the home page again. 6) enjoy!
I thought of remixing this by seeing @broken-deagle 's project, @diamond snake - clone testing