Kangaroo Defense is a chess opening with the ECO code A40. It goes 1. d4 e6 2. c4 Bb4+. White opens with 1. d4 (the queen's pawn) and Black answers 1... e6. After 4 moves it is White to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
The moves
1. d4 – White plays the pawn to d4
1... e6 – Black plays the pawn to e6
2. c4 – White plays the pawn to c4
2... Bb4+ – Black plays the bishop to b4, giving check