(bind-func xtm_light_power
  (let ((lights:xtm_lights* null))
    (lambda (light:i32 power)
      (set! lights (xtm_get_lights))
      (if (> light (tref lights 9)) (tset! lights 9 light))
      (set! light (- light 1))
      (if (or (< light 0) (> light 9))
          (begin (printf "No such light!\n") void)
          (begin (pset! (tref lights 6) light power) void)))))