That is how it works, but it isn't a game, it's the basic rule of finance. Children like Gabriel are learning the high-tech way according to Jayne Pearle, a financial parenting expert.
"Cashless kids are the wave of the present and the future. It's here," Pearle said.
Pearle says today's kids are the first of the "paperless money generation". They often monitor savings and spending with a simple swipe or click.
She says while there are many potential benefits to digital finances such as instant transfer of funds, or the ability to view balances anytime anywhere, there is a potential downside, "I think, especially with younger children, they really don't understand what they can't see and touch."
Pearle says it can be tough to get kids to realize numbers on a screen equate to real money.
Greenbaum says pulling out the plastic put him $200 in debt, "You don't really know how much money you have unless you're constantly checking your phone or your account."
"The lesson he learned is just to be on top of that. It's a great lesson," said Greenbaum's dad, Bob Lancer.
Pearle agrees but says it is critical to make sure kids know it's not only easier to lose track of balances but also extra fees and more.