A run is a loop, not a level
The official description compresses the game into five beats: “DROP INTO THE SHAFT / GUN DOWN THE HORDE / CRACK OPEN EPIC LOOT / STACK ALL UPGRADES / GO DEEPER. DIE. RUN IT BACK.” Every guide on this site optimizes one of those beats. The beginner guide sequences them for a first descent; the controls page removes friction from the shooting beat; the boss reference covers the moment the horde stops being the threat. None of them invent mechanics the game has not shown — the 50-player servers, the current for-all save rule, and gun mastery are all documented on their pages.