In this tutorial series, you'll learn how to create a Bloons Inspired game. The objective of the game is to shoot at the balloons to pop them all...Read on!
Step 1: Application Overview
Using pre-made graphics we will code an entertaining game with Lua and the Corona SDK API's.
The player will be able to shoot an acorn at the balloons by touching the screen to charge and releasing to shoot. You can modify the parameters in the code to customize the game.
Step 2: Target Device
The first thing we have to do is select the platform we want to run our app within. By doing so, we'll be able to choose the size for the images we will use.
The iOS platform has these characteristics:
- iPad: 1024x768px, 132 ppi
- iPhone/iPod Touch: 320x480px, 163 ppi
- iPhone 4: 960x640px, 326 ppi
Because Android is an open platform, there are many different devices and resolutions. A few of the more common screen characteristics are:
- Google Nexus One: 480x800px, 254 ppi
- Motorola Droid X: 854x480px, 228 ppi
- HTC Evo: 480x800px, 217 ppi
In this tutorial, we'll be focusing on the iOS platform with the graphic design, specifically developing for distribution to an iPhone/iPod touch, but the code presented here should apply to Android development with the Corona SDK as well.
Step 3: Interface
A simple and friendly interface will be used. This involves multiple shapes, buttons, bitmaps and more.
The interface graphic resources necessary for this tutorial can be found in the attached download.
Step 4: Export Graphics
Depending on the device you have selected, you may need to export the graphics in the recommended PPI. You can do that with your favorite image editor.
I used the Adjust Size... function in the Preview app on Mac OS X.
Remember to give the images a descriptive name and save them in your project folder.
Step 5: Sound
We'll use Sound Effects to enhance the feeling of the game, you can find the sound used in this example in Soungle.com using the keyword pop.
Step 6: App Configuration
The config.lua file will be used to make the application go fullscreen across all devices. This file shows the original screen size and the method used to scale that content in case the app is run in a different resolution.
application =
{
content =
{
width = 320,
height = 480,
scale = "letterbox"
},
}
Step 7: Main.lua
Let's write the application!
Open your prefered Lua editor (any Text Editor will work, but you won't have syntax highlighting) and prepare to write your awesome app. Remember to save the file as main.lua in your project folder.
Step 8: Code Structure
We'll structure our code as if it were a Class. If you know ActionScript or Java, you should find the structure familiar.
Necesary Classes
Variables and Constants
Declare Functions
contructor (Main function)
class methods (other functions)
call Main function
Step 9: Hide Status Bar
display.setStatusBar(display.HiddenStatusBar)
This code hides the status bar. The status bar is the bar on top of the device screen that shows the time, signal, and other indicators.
Step 10: Import Physics
We'll use the Physics library to handle collisions. Use this code to import it:
local physics = require('physics')
physics.start()
Step 11: Game Background
A simple graphic is used as the background for the application interface, the next line of code stores it.
-- Graphics
-- [Background]
local bg = display.newImage('gameBg.png')
Step 12: Title View
This is the Title View, it will be the first interactive screen to appear in our game and these variables will store its components.
-- [Title View] local titleBg local playBtn local creditsBtn local titleView
Step 13: Credits View
This view will show the credits, version, and copyright of the game. This variable will be used to store it.
-- [CreditsView] local creditsView
Step 14: Game View
The game view is composed by the TextFields that store the score, targets, and available acorns. It also displays the balloons, a restart button, and the squirrel that shoots the acorns. Add the following lines to your code to handle these elements. The squirrel and acorn graphics are from openclipart.org.
-- [Game View] local gCircle local squirrel local infoBar local restartBtn -- [TextFields] local scoreTF local targetTF local acornsTF
Step 15: Variables
These are the variables we'll use. Read the comments in the code to know more about them, some of their names are self-explanatory so there will be no comment there.
local titleView
local credits
local acorns = display.newGroup() -- stores the acorns thrown
local balloons = {} -- stores the balloons in stage
local impulse = 0 -- used shot the acorn
local dir = 3 -- default direction of the acorn
Step 16: Code Review
Here is the full code written in this tutorial alongside with comments to help you identify each part:
-- Balloons Physics Game
-- Developed by Carlos Yanez
-- Hide Status Bar
display.setStatusBar(display.HiddenStatusBar)
-- Physics
local physics = require('physics')
physics.start()
-- Graphics
-- [Background]
local bg = display.newImage('gameBg.png')
-- [Title View]
local titleBg
local playBtn
local creditsBtn
local titleView
-- [Credits]
local creditsView
-- [Game View]
local gCircle
local squirrel
local infoBar
local restartBtn
-- [TextFields]
local scoreTF
local targetTF
local acornsTF
-- Load Sound
local pop = audio.loadSound('pop.mp3')
-- Variables
local titleView
local credits
local world
local acorns = display.newGroup()
local contacts
local balloons = {}
local impulse = 0
local dir = 3
Next Time...
In this part of the series you've learned about the interface and the basic setup of the game. Stay tuned for part two, where we will handle the logic of the application, buttons behavior, and more. See you next time!
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