The reciprocal is your heading ± 180° — the way back. The fast mental method:

• Heading under 180°:  HDG + 200 − 20
• Heading over 180°:  HDG − 200 + 20

Golden rule: the last digit never changes. Reciprocal of 167 is 347.

How to play. Each round is 12 questions. Start in CADET mode, move to PILOT when the conversions feel automatic, then try TOWER — timed ATC calls with bonus points for the edge cases. Beat the top 10 and you'll be invited to add your callsign to the leaderboard.