Card levels and XP

Cards earn experience by playing and practising. Each level adds 5% to the points the card scores, up to level 20.

Levels

A new card starts at level 0.
The maximum is level 20.
Each level adds +5% to the card's modifier, so a level 20 card scores double.
A card's level never goes down.

The card's page in the game shows its current XP and how much is needed for the next level.

The XP of a Tournament Week is added to the card when you claim the reward. Here it takes the card to the next level.

Source	XP for the card
Playing a Tournament Week	50 XP + the points the card scored that week (rounded up)
Practice	60 XP for each 24-hour practice
Fusion	Half of the XP of each card merged into it

Tournament Week XP is added when you claim the week's reward.

Level, XP and fusion are part of the card itself. If the card is sold, its new owner receives it with everything it has earned.