You may notice that you have two kinds of balances on your profile: normal balance and the so-called provisional balance. Provisional balance is like normal balance, but with one exception: you cannot withdraw or tip this balance. Provisional balance can be awarded during special events, as a sign-up bonus, or as winnings in a Faucet playground.
When you join a paid playground, you will use your provisional balance first, and your normal balance after the provisional balance runs out. The idea behind this is that we want to be able to give awards that incite people to play together. Once provisional balance is used to buy in to a paid game, it is turned into normal balance, which can be won by anyone.