Channel IDs of empty (i.e., dead) tiles are color-coded red.
Live cells with identical Channel IDs are color-coded with identical (but arbitrary) grayscale values.
Signals data is double buffered.
Signals 1 and Signals 2 correspond to Level 1 signaling
while Signals 3 and Signals 4 correspond to Level 2 signaling.
Playing from just one buffer will render signal patterns at
just odd or just even updates.
To view consecutive updates, alternate stepping a pair of buffers.