There exists a common concept in level design by the name of flow, used to describe how intuitive a level is to play and navigate. Like a system of plumbing, levels with a good flow will naturally direct players to move through them and onward to each connecting section in order of how important each path actually is, without needless confusion or misleading design. A lot of this comes naturally – it’s common sense that the massive antechamber with a towering steel gate flanked by pits of formless black nether-fluid houses the throne room of some elder god, while the little crack in the wall at the top of a stack of barrels is likely hiding a secret stash of loot in a single dead end room. This also ties into layout design; doors directly across from room entrances are most commonly the way forward on a given path, while things above or far below players are much less likely to be noticed, and the quickest route somewhere is going to be the one most frequently traveled (good logic for designing traps and sneaky alternate paths).
In essence, it’s the estranged game-designing cousin to Feng Shui – everything in its rightful place. The real mastery of flow, however, is a great deal more nuanced than just geometry. Use of lighting, colour, visual themes, and also the learned behaviour of game mechanics can be used to direct players to where they should be going with an unseen hand. Should your game be all about rolling down a hill or falling for instance, the way forward should usually be down a slope, while any detours will split off on a level plane. It’s the sort of infinitely complex discipline Valve tests relentlessly in their games and casino architects leverage to frightening effect.
Sonic the Hedgehog games have a persistent theme of placing a high-difficulty route at the top of the level full of extra lives and powerups which players can strive for while constantly moving forwards. Because gravity naturally pulls them towards the bottom of the stage and fighting it is always rewarded, the end result is a natural flow: higher means harder jumps and better loot; lower means less reward, but safer and easier. Less skilled players naturally get pulled towards an easier path each time they fall, while ones looking for a challenge can always fight their way skyward for greater risk and reward. Good flow is all about making players aware of their options.
Above: The Spoils. Below: Gravity.