The layout of the mansion and its devious puzzles are (as far as my memory can tell) identical to the GameCube version. Which is to say: This is one convoluted-as-hell bit of architecture. Exploring the mansion is handled in third-person with fixed camera angles, and in addition to dodging zombies, you need to solve obscure puzzles and track down a frankly alarming number of different keys to different doors.
While the arbitrary, adventure game-style puzzles can be difficult to parse, the way they send you ping-ponging back and forth through the mansion is actually a good thing. Resident Evil builds its setting up as a memorable place where — despite its absurd layout — I eventually memorized each hallway and especially the location of rare safe rooms. I inevitably needed breathers from the onslaught of zombie attacks, but the game makes you earn them.
Despite the overwhelming forces stacked against you, Resident Evil is not an action game. Even on the easiest difficulty, Jill and Chris can only take a couple of direct attacks from zombies before they fall dead. And even if they were hardier, the mansion contains a very limited amount of weaponry and ammo.
Instead of opting for combat every time, survival depends on making difficult calls about which situations you can escape from and which require the use of force. These split-second choices build an incredible amount of tension, making the game scary on a mechanical level.
It's important that these characters aren't the traditional near-invincible video game heroes; any individual encounter could as soon lead to their death as any sort of brief victory. Opening every new door became a heart-quickening experience, as I dreaded finding out what waited to hurt me on the other side.