A few hints, in order of revealing more, it took me a while to figure out, but I felt quite satisfied when I did:
1. Use audio
2. Listen carefully to a difference in sounds
3. Alternate between left and right
4. Next one will be a full explanation
5. Start pressing left arrow, listen to the sound. When it turns red directly, start with right. Then keep pressing the same direction until you hear a higher / louder beep. Change to the other direction, until you hear that same different beep. Repeat until it turns green and press 'up / forward'. Bingo!