Complex sentence: Black cannot escape check, as he could in normal chess, with Ke7 or Kf7, as these moves do not cross a grid-line, but he can play Kd7 and also Kd8, bringing the king into the same large square as the rook.
Split into simpler sentences: Black cannot escape check as he could in normal chess with Ke7 or Kf7, as these moves do not cross a grid-line. He can play Kd7, however, and also Kd8, bringing the king into the same large square as the rook.