What is XP?

[poofaffy]

What is XP? I see that I get it when the game ends but what does it do? I also don't know what they mean by getting the first star on a card

[[S8] Walt]

XP are points earned by various means through out gameplay. You collect XP so you can level up and unlock more rooms. To check your level you can view your in-game profile by tapping on your name. In order to get Stars in a specific room, you need to keep playing the room. You can check your progress to earn a Star by checking the yellow bar underneath the Stars when in the room selection screen.