section-04

Create your own game: Explorer

So far you have learned a lot about making games. One thing that's come up over and over again is that we've also done a lot of re-typing the same things over and over again. Some of you were even able to just copy and paste, then edit the new copy. However, this style of coding is prone to errors. And when you want to change one thing, you have to change it in a bunch of different places. Then forgetting to make the change once results in really strange bugs.

We have also seen that Corona has packaged up some common things such as shapes and text in libraries that we can take advantage of. Libraries in Lua and some other languages are called modules In this session we'll explore how to create and use our own modules using code from some of our previous games.

Getting the game template

We've set up a game template for you that has the simplified configuration and build settings we created last week as well as the grid, controlpad, and character libraries that were extracted from robotfindskitten and speedmaze.

You can grab an empty starter template from here or begin from my very simple explorer game Colorado Smith.

Learning how to use the libraries

Just like Corona SDK's documentation is available at http://docs.coronalabs.com the documentation for our libraries both on GitHub at https://github.com/coderdojosv/corona-game-template/blob/master/docs. You can also read the documentation by opening any of the files in docs using your code editor.

Open the documentation for the grid module and try to add a grid to your new game.

Example uses

This section has some examples using the provided modules. None of the examples are full programs but they should give you a good idea of how to use them in your own games.

Checkerboard Grid

Here's an example of a checkerboard map using the grid module if you wanted to create a Chess or Checkers game instead of an exploration game.

local grid = require("grid")
local gamegrid = grid.newGrid(8, 8, 700)
gamegrid:eachSquare(function(gridSquare)
	-- Tests if the square is "even".
	if (gridSquare.x + gridSquare.y) % 2 == 0 then
		gridSquare.displayObject:setFillColor(255, 255, 255, 255)
	else
		gridSquare.displayObject:setFillColor(0, 0, 0, 255)
	end
end)

Robot explorer

Here's an example of creating a robot explorer using the character module and placing him on the grid. If a canEnter method is defined on the robot, it is automatically used by the enter method. Otherwise characters can enter any grid square.

local character = require("character")
local robot = character.newCharacter("robot.png")
robot.canEnter = function(robot, gridSquare)
	return not gridSquare.obstacle
end
robot:enter(grid[0][0])

Controller pad

This example, taken from Colorado Smith moves the player character and lets the enemy take a turn.

local controls = controlpad.newControlPad(0, 500, 100)
controls:whenUpPressed(function()
	colorado:enter(colorado.gridSquare:above())
	enemyTurn()
end)
controls:whenDownPressed(function()
	colorado:enter(colorado.gridSquare:below())
	enemyTurn()
end)
controls:whenLeftPressed(function()
	colorado:enter(colorado.gridSquare:left())
	enemyTurn()
end)
controls:whenRightPressed(function()
	colorado:enter(colorado.gridSquare:right())
	enemyTurn()
end)

Other modules

Corona SDK has quite a few interesting modules that we haven't even mentioned yet. The Corona documentation has the full list of Corona modules for you to browse. I think the most interesting ones are

• widget for creating many kinds of interactive tools like color pickers and buttons
• physics for creating screen objects that act according to realistic simulated physics
• storyboard for switching to different levels or scenes in a game (I used this module in the introductory game)
• transition for adding sophisticated animation to on-screen motion

Whenever you use a module it takes time to get used to it. Don't be discouraged by how difficult things seem at first. Imagine trying to do this section on the very first day. It probably would have felt impossible but you've been learning this entire time and even though we're nearly at the last section you will still be learning constantly for the entire time you're a programmer.