DOOM Eternal

• While you unlock Fast Travel near the end of stages, it isn't permanent - it just lasts until you exit that level. If you miss a collectible and want to go back at a later point, you'll have to replay the level entirely.

• In single player mode, you can repeat any level with all your acquired weapons and upgrades. It's best to do this in between levels because you'll lose your progress in the current level when you do it.

• You don't need to complete a level in order to save any upgrades, collectibles, weapons, completed challenges, etc. that you find. They're saved to your profile immediately upon acquisition. This is most relevant if you're replaying levels for things you missed.

• There are no collectibles that are reliant on upgrades that you'd get in a later mission, so whatever mission you're on you should be able to get 100% of everything without having to come back to it later.

• The Master Levels are meant as "end-game" content and I wouldn't bother attempting them until you've got every weapon/upgrade and know how to take care of every type of enemy. You will get introduced to enemies, upgrades, and weapons gradually in the campaign, whilst in a Master Level they just throw everything at you at once. You have been warned!

• If you don't want to sign up for a Bethesda.net account, you can play the game offline. You'll need to load the game the first time with an internet connection, get to the Sign Up screen, quit the game, and then run it again without an internet connection. You can make this easy by using the "Windows Defender Firewall with Advanced Security" application to turn off the connection specifically for the Doom Eternal EXE.