MAP17: Watch Your Step (Doom 64)

MAP17: Watch Your Step is the seventeenth level of Doom 64. This level introduces the Cyberdemon. It uses the music track "Blood Red Shadows" by Aubrey Hodges. The music for this level is unique to Doom 64, where dramatic synth notes mix with dark droning effects to create a tense mood and atmosphere.

It appears to be a transitional/boss level due to its design, including providing all weapons to the player and having a large arena where waves of enemies appear, with a Cyberdemon at the end.

Walkthrough
It begins in a large, empty arena-like area, with a sealed-off exit and a hallway. This hallway contains various weapons, including a BFG 9000, and leads into a square room with an elevated area in the center. Ammo is strewn about, and the area is devoid of enemies, until the player steps on certain tiles. If the player doesn't "watch their step", they will be hopelessly swarmed with demons. The level ends with a huge battle against wave after wave of demons, culminating in a battle with the Cyberdemon. Two of them are fought simultaneously on the Watch Me Die difficulty.

Secrets

 * 1) After opening the gate door and killing the Pain Elemental behind it, go up either elevator. Go through the yellow teleporter up here, but stop moving after you go through. Now simply shoot straight ahead with a shotgun or chaingun, then back up, and you'll get the first secret. Turn around and make sure you activate the switch in this little room before leaving too.
 * 2) The other secret is activated in the same way as the first secret. The grey hallway that you teleported to in secret #1 has a brown door on each end of it, and both of them are the secrets. When you shoot one brown door, the door at the opposite end of the hall opens. So for the second brown door, head over to the teleporter next to it, go through, then go through again, and you'll be facing straight down the hallway like you were in secret #1. Shoot (the door), back up, then turn around and hit the switch. Just entering these two rooms will give you 100% secrets, but the two switches you activated in these rooms open up another passageway earlier in the level that lets you access that Megasphere you saw earlier, as well as an Invulnerability sphere.