2D Boundaries

One problem that will appear when making 2D games, especially those seen from a side view, is how to differentiate between tiles or zones you can pass through and those you can't.

The simplest way of doing this is to use high contrast colors to define these areas. Let's look at a few examples.

In the first image below you'll see a screenshot of "Gunpoint" by Tom Francis. This game makes it explicitly clear where you can and can not travel by using contrasting brightness in background elements. The darkened, impassable, wall tiles and the much brighter rooms the action actually takes place in are almost black and white. You couldn't make the

Note that in the case of "Gunpoint" the dark areas still have some artistic detail within them. We can still see what the walls and floors are made of because they are using colors that are still in the same dark scheme as the walls and floors themselves.

"Stealth Bastard" by Curve Digital is another game that uses such an approach. Note again how the thick black divisions between traversable areas makes it clear where you can go even though, unlike gunpoint, the game has a much darker atmosphere. Even with the shadowy environment it's obvious where you can and can't go.

In the last example let's look at "Mark of the Ninja" by Klei Entertainment.

This game shows how you can use high contrasting imagery but still make that imagery detailed and shake off the "blocky" nature of the last two examples. Notice how there are several parts of the level which are pitch black but where it should be obvious that you can pass through. The vertical struts for example. Part of what indicates these architectural elements are still passable is their thin and porous nature. They don't have a "solid" feel.

At the same time the outer walls are still black, but also very thick, indicating that they can not be traveled through.

While these are very obvious examples one should not think that thick, high contrast areas can be the only indicator of movement boundries. There are times when we want a division that clearly indicates some kind of interaction with objects in play but not be a complete boundry to all interaction.

For instance, take some of the early levels of Nintendo's "Super Mario World". This game contains several stages where there are platforms that can be stood upon but do not completely inhibit movement. Aside from jumping onto them from the side you can also jump up onto them from *underneath* the platform and land on top without falling down through the platform.

Note how in the screenshot to the right we see platforms of vibrant color and thin black outlines which characters can stand on. But at the same time there are blocks which we can *not* pass through. You probabaly don't even need them to be pointed out to you. The mere "solid" nature of their appearance makes it clear you won't be going through them.

The language of Super Mario World is simple:

  • High Contrast lines denote some inhibition of movement.
  • The thicker the object the more movement will be inhibited (from passing through in one direction to not passing through at all).

A game might have several ways of indicating this to the player early on.

  • It might contrive to force you to jump, perhaps with an approaching enemy, so that you'll land on one and learn that it is a walkable platform.
  • It might place an enemy or NPC on top of a walkable platform which will give the player themselves the idea that it can be walked upon.

In the screenshot to the right you can see the first screen of the first level of the game where both of these possibilities are presented. In this first sequence a diaper-donned turtle can be seen on an inclined platformInclines were also new to the series. Oh what an amazing time it was., indicating that the surface can be stood upon, and the forward motion of the enemy will force the player to jump, possibly placing the player on the platform.

If you play the game you'll realize fairly quickly that this pattern follows throughout the entire game. It does not matter what the theme or color scheme of a level is, all levels within the game will follow the previously mentioned guidelines to show the player where they can and can not go.