Heads or Tails

prefix is .

When the command 'coinflip' is entered, the bot will generate a random choice between 'heads' or 'tails' and post this to the channel. If the generated result is 'heads', the user who entered the command is the winner. If the result is 'tails', the user mentioned in the command is the winner. The bot then pings the winner and tells them that they won the coinflip.