colorRamp(...)
attr x = colorRamp(...)
@StartRule
Lot --> Tower(10)
Tower(n) -->
case n == 0 : NIL
else : primitiveCube(1.5, 0.8, 1.5)
colorRamp(n / 10, "red", "yellow", "green")
t(0, 0.9, 0)
Tower(n - 1)