RAIN(6) BSD Games Manual RAIN(6)
rain -- animated raindrops display
rain [-d delay]
The output of rain is modeled after the VAX/VMS program of the same name.
To obtain the proper effect, either the terminal must be set for 9600
baud or the -d option must be used to specify a delay, in milliseconds,
between each update. A reasonable delay is 120; the default is 0.
Eric P. Scott
BSD May 31, 1993 BSD