Complex sentence: The gameplay consists of elements of first-person shooter and action-adventure game with restricted movement (i.e., "on rails")--rather than allow free motion, the game limits the on-screen character to predetermined paths through the environment.
Split into simpler sentences: The gameplay consists of elements of first-person shooter and action-adventure game with restricted movement (i.e., "on rails"). Rather than allow free motion, the game limits the on-screen character to predetermined paths through the environment.