Core gameplay x Map gameplay. The distinction that Hourences make is pretty clear. Core is about the game's rules and to what extend the player can interact with the game's world. Map is about placing challenges that are specific to that map and the player has to use the powers and abilities that the game provides to pass a level or a certain area. Both are intertwined and for the good they can't be split from each other.

Let's say you have a superhero with the power to fly. If the level is all indoors with no opportunity to fly at all we have a mistake. The exception is when we have strong storyline reasons to do that. And we also have the opposite. If the player can fly over all obstacles and skip them, the map's gameplay is not correctly intertwined with the core's gameplay. To give a very simple and crude example: there are games with modding tools such as Unreal Tournament. Some servers run mods that multiply health by 10, add automatic regeneration and infinite ammo. The player's experience is mostly ruined because the player lose the challenge with infinite health and ammo. I have played a mod called Monster Hunt and most servers run that infinite ammo and health mods that make all maps lose their challenge because the server is changing the core aspects of the game. How does some level designers compensate for that? Some of the maps designed for Monster Hunt and with infinite ammo and health in mind employ bosses with extra high health, traps that deal a lot of damage and obstacles that are just plain impossible to pass if the server is not running the infinite ammo and health mod. See how the core gameplay ends up being tied to the map gameplay?

Any game with puzzle solving emphasis is a great example of a combination of map gameplay and core gameplay. In the 2D sidescrolling world we have examples ranging from Prince of Persia, Super Mario, Sonic to Trine and Shoot em Up (shumps for short). Think about Super Mario. In all levels there are bricks which the player can break. Some specific levels have map specific mechanics such as flying or swimming. Think about Shoot em Up such as R-Type series with its multiple weapons. One weapon fires laser beams that ricochet from walls and some levels are designed with walls for that weapon. Sonic is another great example because some specific levels present map specific gameplay, such as flying with air currents or using an air bubble shield in underwater levels.

In the 3D world great examples come from Bioshock, Jedi Knight, Tomb Raider and other games. Lara Croft can grab on ledges, swim, jump high, escalate walls, swing on ropes, crawl and some other abilities. The levels in the Tomb Raider series focus on one or more of those Lara's abilities to present challenges for the player to solve. The Jedi Knight games do the same thing. Each level presents challenges that the player has to pass by taking advantage of the Jedi powers. There are even twists that happen in unexpected ways. Unreal Tournament and Urban Terror have servers dedicated to the art of jumping. There are those racing tracks where the player has to use their jumping and hopping skills to traverse various obstacles. Some of those obstacles even defy the laws of physics and that's due to game's simplified physics model, which sacrifices realism and priorizes the gameplay.

Mark Rosewater talks about designing for Magic the Gathering and he says that designers often have a big ego and attempt to please themselves. That's a mistake! Your audience is to be pleased by you, not yourself. The mechanics and gameplay are meant to be played and experienced by your audience. There is an important aspect that he talks about that is how the player feels the game and bad mechanics lead to bad gameplay. In MTG there are quite a few mechanics that were dropped over time because they were harming the game. In level design and game design the same mistake can happen.

Over the years MTG has shifted its focus from some types of cards towards others. For example: they decided that players should be able to interact with each other and this means that cards with effects that completely block out all spells should not be common. They want players to have answers to threats and the answers themselves have the risk of becoming even bigger threats. That's a very hard balance to achieve and MTG constantly faces player's dissatisfaction over that issue. About gameplay I'd argue that we very much face the same issue. Players want to interact with game world but at the same time, some types of interaction may be undesirable or even become boring over time. One quick example is elevators or lifts. If the speed is too high or too low it may impose problems for the player for which he or she cannot solve because they were programmed that way.

Abstract floorplan x Realistic floorplan. The way Hourences distinguishes the two is pretty much the same idea that Mark Rosewater has when talking about Top down vs Bottom up design. Are you going to priorize mechanics and gameplay first or aesthetics and theme first? I'd argue that there isn't a perfect balance between the two and more often than not games adopt both strategies in their levels. As the name implies, realistic is about real world settings. Think about hospitals, cities, subways, office buildings and so on. Abstract is more about alien worlds, fantasy realms or anything that wouldn't be built in the real world.

The point that I'd make here is that the easiest concepts to grasp is by either going full abstract or full realism. For example a subway system for Counter Strike. The setting is pretty clear in terms of atmosphere and feels. Now if you think on Lord of the Rings movies, a fantasy realm floorplan has more freedom in terms of concessions as realism is not necessarily the main goal. The more difficult place to be is when floorplans are hybrid, somewhere in between abstract and realistic. This is the case of games such as F.E.A.R. 2, which blends realistic environments with horror themes.

Realistic doesn't necessarily means feasible or an exact copy of a real world setting. By that I mean that there are concessions made due to gameplay. For example: in a real world bathroom there is only one door to enter or exit. In a game world, however, we can have two doors and even some third entrance with a ventilation system for example. It depends on the gameplay. Conversely, abstract doesn't mean that we are free to do whatever we want. We can have floating islands or castles if we want to. But there should be a good excuse for that. Either story-wise or gameplay-wise. The point that I'm making is that even in an abstract world we are unconsciously comparing it against common sense and the real world, meaning that if there is something off, the players are going to notice it. For example: if the level is the inside of a spaceship, it has to convey the interior of a spaceship as obvious as it may sound.

If I were to compare to architects and engineers of real world structures I'd say that there are some similarities with level design. For example: when engineers project a subway system there are concerns about capacity and space, which are more or less the same within a game world. However, a key difference is that the game world is tied to its gameplay and trying to build an exact copy of a real world subway system with real world measures won't work. Vending machines inside subway stations are always located near the stairs, entrances or exits, never far away at the platform's end. In game setting that's not always the case if there is a reason to place a vending machine at the platform's end for example.

I personally think that building game worlds is similar to an architects or engineers job. In a real world hospital the floorplan has to account for emergency exits, the flow of people, contamination risks, safeguarding measures against fire, etc. In a game world we have to account for who is going to play there and what gameplay is to be expected. I completely agreed with Hourences here in saying that the better your plan is to begin with, the better you are are foreseeing possible problems ahead of time.