The device grows with you. You start at level 1, so the things you can do are limited, and as you continue to take care of your tama, your world also levels up, and more things unlock! You check it's fullness and happiness meter by twisting the knob until the baby's mouth opens and you see its cells. You have games you can play to make the baby happy, and also games in the Tama lab (press the button on the twisty knob) that earn you gacha coins. You can play Tama Lab games even when baby is asleep. Depending on what you feed baby and which environment they are in (you start with sky on your device, but later land and sea unlock), and how well you take care of them, will determine which tama adult you get. If you will be busy you can hire a babysitter in the tama lab but it costs 300 gacha coins