Question

To make this task manageable, we will radically simplify the concept of a world. Namely, a world will be a two-dimensional grid where each entity takes up one full square of the grid. On every turn, the critters all get a chance to take some action.

Thus, we chop both time and space into units with a fixed size: squares for space and turns for time. Of course, this is a somewhat crude and inaccurate approximation. But our simulation is intended to be amusing, not accurate, so we can freely cut such corners.

We can define a world with a plan, an array of strings that lays out the world’s grid using one character per square.

var plan = ["############################",
            "#      #    #      o      ##",
            "#                          #",
            "#          #####           #",
            "##         #   #    ##     #",
            "###           ##     #     #",
            "#           ###      #     #",
            "#   ####                   #",
            "#   ##       o             #",
            "# o  #         o       ### #",
            "#    #                     #",
            "############################"];

The “#” characters in this plan represent walls and rocks, and the “o” characters represent critters. The spaces, as you might have guessed, are empty space.

A plan array can be used to create a world object. Such an object keeps track of the size and content of the world. It has a toString method, which converts the world back to a printable string (similar to the plan it was based on) so that we can see what’s going on inside. The world object also has a turn method, which allows all the critters in it to take one turn and updates the world to reflect their actions.

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.