Fu

Fu (符) are small structural points added to your Riichi score. You start at 20 fu base, then add 2 for a closed pung of simples, 4 for a closed pung of terminals/honors, 8 for a concealed kong, 2 for closed-wait/edge-wait/pair-wait, 10 for a closed-hand ron, and so on. Fu rounds up to the nearest 10 and multiplies into your han: total points ≈ fu × 2^(han+2). Pinfu is special — it caps fu at 20 (closed ron) or 20 (tsumo).