Your goals is keeping the garden alive. For that purpose you have to provide water, sun and soil before the bars run dry. Using Z, X and C at the appropriate time will trigger a card which will refill one of the bars by a little amount (Z for water, X for sun and C for soil). The amount of that refill corresponds to the value of the card (1 to 3).

Be aware of the cards because each one will have a different speed and might throw your rhythm off balance! https://ldjam.com/events/ludum-dare/41/nun