It occurred to me that most of what I post here is common sense. This is good - it means you don’t need a degree to know it or use it, just a little bit of sensible thought. Which is why I’m now going to cover another common-sense tactic.
Everyone has played a map that seemed excessively difficult to worm through, despite more complicated maps being no problem at all. Everyone has had the brief moments of frustration from trying to get from A to B via C, just to find that you can’t get from A to C, or that C doesn’t exist at all and you’ll have to find D, E, F and G. Sometimes, it seems that you’re stuck at A and there is no where to go.
The problem is only further amplified when C (or D, E, F and G) looks so promising, but when you get to it find it doesn’t help you get to B at all.
Forget the letters. Remember this: players like to know where they’re going and they like multiplayer maps to be intuitive.
This means making doorways, pathways, halls and crevices that take the player somewhere else very easy to see. I’ve mentioned this before, but the general rule is that the player should be able to see an exit as soon as they enter a room. There should always be some obvious way to make progress through the map, or at least a route away from where they are or have just been. This is one of the founding principles for ensuring that maps flow and that players flow through the map. No one likes having to stop, turn round, and go back the way they came because they couldn’t see where to go.
This does of course bring up some issues, particularly when it comes to making environments look real. Real places have lots of dead-ends and locked doors, but in real-life we have the time and patience to check them. In a game however, we don’t. The skill here is to make sure that only the useful ones grab the attention of the player, through lighting, size, design, style and/or position. Often, just lighting and position will do. Obscuring the feature in shade or having it located in an out-of-the-way place is enough for the player to realise it’s not any use to them. Similarly, directing the player’s eye to important features, by lighting well or using environmental cues, will help the player work out where they can go.
Some cues are fairly obvious but very powerful. The oldest and still one of the best has been around since Doom: you’ll find that players will typically try to follow paths that adopt a similar ground style/colour/texture to the ground on which they’re currently standing. A big change in the texture or colour of ground typically indicates a boundary, and suggests that it will block progress. The subconscious thinking is a little like this: “If I keep walking on this colour floor, it’s more likely to take me somewhere I recognise.”
The key here is to avoid frustration. A player can take being frustrated at bad level design a couple of times, but any more and they will start giving up. When you’ve got everyone doing this, the map becomes unplayable. Since level design is all about 3D space, making sure players can navigate it easily is obviously important.