There's a working archive of them here: http://www.effectgames.com/demos/canvascycle/
They're real masterpieces. 256 colour pixel art, with some colours palette cycling to create animation by using the right pixels in the right place. But then he also changes the palette to create different times of day.
Some of them have rain or snow and the particles appear to move smoothly over the various parts of the background. Carefully switching the palette index not just for each bit of movement but also using a different section of the palette each time a snowflake transitions to pass over a different-coloured background layer.
There's a pool with a shimmering reflection! There's an animated aurora borealis! There's underwater scenes, oceans, fires, all animated via fixed palette cycling only!
And none of it looks forced, it all looks beautifully natural. You can open up the "Options" tab to see the palette and hover over the colours to see where they're used.