     // under top rung
          0, -1, 0,
          0, -1, 0,
          0, -1, 0,
          0, -1, 0,
          0, -1, 0,
          0, -1, 0,

          // between top rung and middle
          1, 0, 0,
          1, 0, 0,
          1, 0, 0,
          1, 0, 0,
          1, 0, 0,
          1, 0, 0,

          // top of middle rung
          0, 1, 0,
          0, 1, 0,
          0, 1, 0,
          0, 1, 0,
          0, 1, 0,
          0, 1, 0,

          // right of middle rung
          1, 0, 0,
          1,