I'll share one of mine as well. It's a 1-d cellular automata simulator that randomly generates rules and tries to use nice colors. Click to see a new one, and the URLs it generates can be shared. However, that is the limit of interactivity (for now, it's actually meant to be a loose clone of Wolfram Tones but that is far from ready).
I like how space key also works and how browser navigation is supported so that when I accidentally click too many times, I can use the browser's back and forward buttons to navigate between recent patterns.
Sorry for the late response, I'm not used to not getting notifications for responses to my comments.
There is no simple way to get the rules for that CA. However, if you press Shift+Space, you get an alternative representation of the hash that lets you re-seed while keeping the same rule: https://skulk.org/cell1d/#c2:3:1,0,0,1,0,0,1,0:12;120;115,15...
This format is ad-hoc, but you can read it as such: The first number after #c is 2, which is the number of states. The second number, 3, is the size of the transition window. This tells us that this is a standard 1-d CA. The next 8 (2^3) numbers is the transition table. Interpreting it as binary (in reverse), we get the number (and rule) 73. http://atlas.wolfram.com/01/01/73/
The next couple of numbers are the colors used, and the final number is the seed. You can change this and the rules/colors will remain the same but the top row is re-randomized.
The basic mode is a matrix of identical tiles spinning at different rates, creating complex organic motion out of a simple concept. There are two other modes and lots of fun parameters to play with!
Some other fun "art toys" I like are:
1. https://29a.ch/sandbox/2011/neonflames/
2. https://codepen.io/davidpanik/full/myMrLx/
3. https://codepen.io/jackrugile/full/DGenc