We look at the squares above, to the right, below, and to the left, and make a string with zeroes if there’s no wall there, and ones if there is. For this, we need to inspect the squares around each wall piece and change the image we use depending on how it’s connected to other wall pieces. What we want, though, is for all the walls to join up with battlements around the outside.

Build a series of walls to safely encircle your fort.ĭuring the draw() function, if we draw a single wall section wherever there’s a 1 in our grid, we’ll see flat squares where the walls are. When we get an on_mouse_down() event, we check that the square we’re over is a 0, and if it is, we switch that to a 1. We track the mouse movement with the on_mouse_move() function and when we have the mouse x and y coordinates, we draw a single section of wall under the mouse pointer locked to the invisible grid. This will stop the player building walls over the fort. Our fort will take up four squares, so we set the top-left square of the fort’s position as 2 and the other three squares as 3.

To define where we can and can’t build, we can load in a little black-and-white image and read pixels from that to set squares which are non-buildable as 3. In this list, we’ll start with all the squares set to 0 and then if we add a wall section, switch that square to 1. If we say that each wall segment is 40×40 pixels, on an 800×600 pixel window we can define a grid that is 20×15 squares in a two-dimensional list.

We then need to define an invisible grid which will hold the details of where the walls are positioned. To start coding, we’ll need a background – in this case, a shoreline section of land. Cannons ready, prepare for battle! It’s the original Rampart, developed by Atari in 1990.įor our Pygame Zero example, we’ll look at two tower defence mechanics: the wall building system and then the check to see if the keep has been enclosed by walls.

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