I am planning a 2-D science fiction game involving spaceships. A major thing that I am having trouble figuring out is how to create a 2-d array of smaller maps that the player can explore.
My inspiration is the Flash game Starfighter: Disputed Galaxy:
The map here is composed of a 2-D array containing smaller maps called sectors. Each sector is connected to surrounding sectors, such that when the player moves to the edge of a sector, they go to the next.
For example, if I was in sector
 and I move up until I cross the edge, I am taken to sector
, then I go to the right, crossing the right edge of the sector, I am now taken to sector
However, if I am at a sector like
 and attempt to go down, It will not allow me to cross the edge line of the sector. In other words, a huge map made out of smaller maps.
I'd like to know how to implement those transitions. How do I programmatically determine which sector to move to (or not allow movement) when crossing over a boundary?