Like just about every other artistic effort in my life, things looked a lot better in my mind than in reality. There is only so much you can do with a 5x5 display, even if it is RGB. As every civilized person knows, an RGB LED is just 3 LEDs in the same housing. With the M5 Atom Matrix, you can sometimes see the individual components of whatever RGB color you've selected. From a distance, it's OK, but up close it's a bit, uh, discrete. In the end, I had to simplify my grand designs so that the displays were more symbolically meaningful and less literally artistic. I didn't have enough pixels for good pointillist artwork. (I had one graphic that was intended to show a match being lit into a flame by an unseen force, but it turned out that I had to explain what it was to my test audience. After I explained it, the reaction was something like, "yeah, I guess it is".)
Itt also occurred to me that I wasn't sure how I was going to orient the M5 Atom Matrix device in its final position. Even the otherwise reasonable "lots of flames shooting up" would look a bit wrong if the tops of the flames went sideways or down. In the end, I decided to use designs that were horizontally and vertically symmetrical, and I achieved some animations using built-in lighting effects provided by ESPhome's FastLED component.
Here are the animations that I finally used. To see the actual animation effects, you should watch the video I provided earlier. These still photos are just for easy reference. My code reacts to button presses of the front face of the M5 Atom Matrix by stepping through the different animations. That's my bony finger doing just that in the video.
The Water Watcher has one additional flame status state that the Water Bug doesn't send. The "startup" state is used when the Water Watcher boots up but before it has received its first MQTT message. I just wanted something visually distinctive, so I used the ESPhome "addressable rainbow" effect.
The "pilot_on" animation is displayed almost all of the time. There are only a few minutes a day when something else is displayed. I could have chosen to just have a blank display, but I wanted to have some indication that the Water Watcher was working and not dead. I settled for flickering dots (using the ESPhome "addressable flicker" effect) in each corner of the 5x5 matrix to imply "a little bit of flame" to suggest the pilot light.
Analogous to the "pilot_on" animation, the "full_flame" animation is meant to suggest "a lot of flame". It uses the same RGB orange color and ESPhome "addressable flicker" effect, but in this case all of the LEDs are involved. (I get to see this display when I step out of the shower.)
I chose to have the Water Watcher give s distinctive display for the "dazzled" state. It's just these five RGB orange pixels in the center of the display, again animated with the ESPhome "addressable flicker" effect. I don't have any illusion that this suggests to anybody else what's going on during the "dazzled" state, but it makes me nerdly happy to be able to see it as a distinct state.
Finally, the reason we're all here: the "pilot_off" state. The animation for this is a lot of blinking and flashing of RGB blue. I wanted it to be very distracting and unavoidable. Even though I told the household members what it means, I expect the normal reaction to seeing it will be to ask me what the heck it is; mission accomplished!
Again, I recommend you watch the short video to see the actual animations. The flickering effect for the flames is fairly effective (and it took some experiments with parameter tuning to get it to be so).