So you see, you're nowhere new, but instead you are in a normal map, just with different tiles.

Secret World 1:

Secret World 2:

Secret World 3:

---

A tile set is a group of all the tiles used in one region. They'll usually have three or four different types of wall blocks, three or four enemies or parts thereof, and about three (at most) background tiles. Because there are so many different tiles in the entire game, the Gameboy cannot keep them all in its RAM at one time, so they come in sets at a time. Only one set is stored in the RAM at one time. When one is being dropped out of the memory to load a new one, you'll notice the screen fade to black and then back in a new area. Note how the new area has a different appearance all together.

The layout of the game map is a set of simple keys whose different attributes call forth the different tiles in the Gamboy's RAM and place them where the keys specify. For example, key A (these are made up) would call for a block for a wall while B would call for a clear black tile, or a background. However, A will call for a wall block in one area while A in another area calls for a background tile.

Now, try to imagine passing between areas without changing the tile set. Where you'd expect to see a wall in the new area, for example, you might see a background instead. Or, where there would normally be a save point, there would be a plant. The map was written to call for something specific, but something else is placed instead.

Since that inevitibly confused you, think if it this way- when in a Secret World, you're in a normal area, but there are blocks and tiles from different areas in it, making it appear to be different. Where walls are replaced with backgrounds, you can pass through to places you couldn't normally get to. I leave the exploration to you.