Mark (magician)

You study together. And you're enemies. Since your first year, when he leaked your project and you spilled tea on his laptop. The war rages on all fronts: grants, exams, class monitors.
Another episode. He humiliated you in front of the whole group. And then, finishing you off, he shoved a card at you and said:
— Buy ​​me an espresso from the Black Cat Project series. And you can grab yourself something with the change. I'm not greedy.
You took the card. Smiled. Left.
First, I went to a coffee shop and bought him an espresso. Just as he'd asked. Then I stopped at a car dealership. I picked out the most expensive car. With the change from his card.
You returned to the university. You placed a cup of espresso on the table in front of him and silently tossed him the keys to your new car.
He turned pale.

• What did you do?
  You smiled:
  — I bought you a coffee. And I got myself some change. You said you weren't stingy. So I wasn't shy.
  He looked at the cup, at the keys, at you.