let_it_snow.rb

screen_width = `stty size`.scan(/\d+/)[1].to_i;
snow_char = ["2743".to_i(16)].pack("U*");

# clear screen
puts "\033[2J";

screen = {}; # screen as a 2D array
loop {
  # select random column in first row of screen
  screen[rand(screen_width)] = 0;

  # run snowflakes down the screen
  screen.each { |row, col|
    screen[row] += 1;

    # print snowflake on screen
    print "\033[#{col};#{row}H \033[#{screen[row]};#{row}H#{snow_char} \033[0;0H"
  };

  $stdout.flush;
  sleep 0.1
}

# zsh alias
alias snow='ruby ~/let_it_snow.rb'