Each round consists of ten tricks:
- The starting player leads with any card.
- If the starting player plays a colour card, the opponent must play a card of the same colour or a Potion card. If they do not have a card of the same colour, they may play any other card.
- If the starting player plays a Potion card, they must announce a colour. The opponent must play a card of the named colour—even if they have a Potion—if they can. If they don't have any of the named colour, they may play any card.
Compare the played cards to determine the winner of the trick
- If both cards are the same colour, the highest number wins.
- If both cards have different colours, the stronger colour wins. (Colour strengths are tracked at the top of the board. The first colour to be played during a round automatically becomes the weakest colour. When a second colour is played, that becomes the middle colour and the remaining colour becomes the strongest.)
- If someone played a Potion, the Potion's effect is resolved, then the highest number wins. (The "+" on the potion cards is basically worth ½: Potion 3+ would beat Red 3, but lose to Red 4.)
The effect of a potion is based on the card played by the other player:
- Purple: winner steals a trick.
- Green: players swap two cards.
- Red: reset the color ranking.
- Potion: they neutralise each other, so nothing happens and the highest wins.
The pawn moves a number of spaces towards Hyde's end of the board equal to the difference between the number of tricks each player won (irrespective of who actually won the most tricks).
The winning condition is different for each player.
- Hyde: if the pawn ever reaches the last space on Hyde's side, Hyde wins immediately.
- Jekyll: if after three rounds Hyde has not won, then Jekyll wins.
- Return Match: players play 1 round as Hyde and 1 as Jekyll. The Hyde uses the least rounds to let the pawn reaches the leftmost space wins.