play.rb

#!/usr/bin/env ruby

KEYS_BY_ACTION = { next: :Right, prev: :Left, toggle: :space }

action = (ARGV.first || 'toggle').to_sym
action = :toggle unless KEYS_BY_ACTION.has_key? action

unless (window = `xdotool search "Google Play"`[0..-2]).empty?
  `xdotool keydown --window #{window} #{KEYS_BY_ACTION[action]}`
else
  `mpc #{action}`
end