# Rain pooling: no input, the scene idles under the default rain (0.35).
# The fluid field (seelie_fluid) accumulates coverage on the receptive
# tiles (deck, banks) at rain*accum - evap = 0.35*0.035 - 0.006 =
# 0.00625/s: ~0.031 after 5s, ~0.125 after 20s. The river tiles are
# sinks, pinned at full coverage from the start.
# frames: 1200
