Let me give you an idea of my skillset. I’m a self taught programmer who mainly uses movie clips and timelines to make my games in Flash. I am not one to use Flex or Flash Builder to set up my projects, I like to see things on the timeline. I learned to program in AS1, switched to AS2, and held out using AS2 for a long time because AS3 was confusing to me, finally I learned AS3 and my skills have slowly improved over the years. I don’t know any other programming languages other than Actionscript, PHP and HTML, basically stuff I need to know for web design.

I’m about a month or so into using Corona and I’ve been able to pick up on it pretty fast. There are some major differences between Lua and AS3 so I’m compiling into a list for other Flash devs who follow in my footsteps. I was scratching my head a few times and there wasn’t really anything out there that I could find that put the differences in plain English. So I’m going to take a stab at it.

Here are some key areas that you might find confusing, I’m going to try to explain them from a AS2-AS3 developer perspective.

File Structure:

With Corona SDK you will always start with a “main.lua” file. This is the starting point for all your coding. You can break up your code into several files to try to keep things neat and tidy by using “require(‘filename’)” this is covered fairly clearly in the documentation of Lua.

You can use the structure defined here to build multiple scenes into your game: http://techority.com/2010/11/19/how-to-use-scenesscreens-in-corona/

However if you to use this be sure to create your global variables in “main.lua” if you want to access them everywhere else. Otherwise your code might error out looking for a variable.

If Statement Structure:

If you are trying to learn Lua you more than likely already noticed this.  If statements don’t need parentheses and they don’t use brackets to enclose the statement.

so this…

if ( !myVar) {
trace(‘Hello, World!’);
}

becomes this…

if not myVar then
print(‘Hello, World!’)
end

Logical Operators:

If statements wouldn’t be very useful without the ability to check multiple things at once.  Remember that Lua uses words rather than symbols for most of these.  So “&&” becomes “and” , “||” becomes “or”, and “!” becomes “not”.    There are several other differences on this so if you want to read about them go here.  http://lua-users.org/wiki/ExpressionsTutorial

Loop structure

Not So Random Numbers:

Random numbers in Flash always seem at least fairly random. However on several devices random numbers are always the same sequence based off a default seed number. You need to change the seed for your random numbers to make sure the numbers are more random. So using a number that will always be different for a seed, like the current time and date will make your random numbers works better.

math.randomseed( os.time() )

Read more here… http://lua-users.org/wiki/MathLibraryTutorial

Missing functions:

This is irksome, things you take for granted in AS3 are missing.  There are quite a few that are either missing or are called by another name.  Here is a quick list of the ones that I’ve come across that I really miss.

Array Funtions:

Arrays in Lua are called tables, and several of the functions that you are used to as a flash developer are not available in Lua.

First off to make a table you simply do this:

myTable = { }

or

myTable = {1,2,3,4 }

or

myTable = {name = value, name = value}

Your table is ready to use. But you don’t have the same tools at your disposal as in Actionscript. You have nothing that works like “pop()” or “splice()”. Here are a few functions you need to be familiar with to work with tables.  Notice that you do not call the name of the table then insert to insert into a table.  You tell the function what table is effected by passing the table name as an parameter.

table.insert( myTable, #)

table.remove( myTable, #)

Here is a link to a pretty good writeup on tables: http://lua-users.org/wiki/TablesTutorial

Comparing tables seems to not work the same way as in actionscript.  I might be doing it wrong but comparing

Continue:

Need to skip to the next itteration of the loop that you are currently running? Lua does not offer this functionality.

Switch statements:

You can’t use switch statements in Lua, you have to either use a massive if else statement, or a table. Here is a link to a better explanation:
http://lua-users.org/wiki/SwitchStatement

There are quite a few other things that I want to point out but this post is getting rather long so I’m going to make it a multiple part post.  Look for more information in the near future in part 2.

In our our recent tutorial on clouds effect via BitmapData.perlinNoise and ColorMatrixFilter, we presented a nice clouds animation but very CPU intensive and not suitable for larger images or for mobile devices. Here we present a version that is extremely CPU efficient, runs very well on Android 2.2, and can be used to generate large images. In the two examples linked below we generate 500 by 380 animations. Click each screen shot or the corresponding text link to open a Flash movie.

Simpler and highly optimized animation:

An interesting two-layered effect:

Download

• Download all source files corresponding to these effects: cloudsfast.zip

How is performance optimized

In our previous tutorial, Realistic White Clouds on Blue Sky in AS3 Flash, we presented a method for producing a continuously evolving picture of white clouds on a blue background, making use of Perlin noise and a ColorMatrixFilter. Although the effect was highly aesthetic, it suffered from high CPU usage due to the repeated Perlin noise computations. We present here a greatly improved method for producing moving clouds, with very light CPU usage, suitable for mobile devices.

This time we have also made the cloud effect easy to incorporate into your own designs, by keeping all the code in an external class called MovingClouds, which extends the Sprite class. The clouds are then a display object, and can easily be added to the Display List.

Creating an instance of the clouds is easy: simply use the constructor as follows:

var clouds:MovingClouds = new MovingClouds(w, h, scrollX, scrollY, useBackground, bgColor);

This creates a cloud display with width w and height h, which will scroll every frame by an amount scrollX in the x direction and scrollY in the y direction. These scroll amounts must be integers, but can be positive negative, or zero. If you wish to have a solid color background behind the clouds, set the Boolean variable useBackground to true, and set bgColor to the color you wish.

About the Code

Instead of repeatedly computing Perlin noise, which is CPU intensive, we have opted for one cloud image which is continuously scrolled. The cloud image is made to be larger than the final display, so that the repetition of the pattern is not noticeable.

To make the cloud image continuously scrollable, we make use of the “stitch” option during the Perlin noise generation. This option creates an image which seamlessly connects the bottom of the image to its top, and its left edge to its right.

Scrolling the image is accomplished using the scroll() method of the BitmapData class. However, this method does not have a built-in option for wrapping one side of the image around to the other, so we manually wrap the image.

Here is how we do the wrapping. When bitmap data is scrolled in the x and y directions, certain portions will be pushed outside of the boundaries of the bitmap. So we copy these portions to other rectangular bitmaps before scrolling, scroll the data, then copy the saved rectangles into the appropriate positions on the opposite sides. This is illustrated in the figures below: three rectangles called horizCutRect, vertCutRect, and cornerCutRect are copied and then moved to new positions horizPastePoint, vertPastePoint, and cornerPastePoint.

This continuous copying and scrolling of bitmap data is very efficient. In our previous example which used repeatedly computed Perlin noise, the cloud displays became very CPU intensive when large bitmaps and a high number of octaves were used for the Perlin noise. In this example, any number of octaves can be used, and the methods allow for a large display.

Layering the clouds

In our second example presented above, we create a very nice effect which suggests three dimensional clouds by simply layering one ScrollingClouds instance over another. We lower the alpha of the top layer, and also use a transparent background by setting the useBackground variable to false in the constructor.

Quoted from http://www.flashandmath.com/intermediate/cloudsfast/index.html:

Basically instead of typing “trace(‘hello world’);” you type “debug(‘hello world’);”.

Then once you are done developing the swf you just change the debugMode variable to false and turn off all your trace functions to save a good bit of processing in the final product. It’s quite handy.

Here is the code I use:

var debugMode:Boolean = true;

function debug(STRING:String){
     if(debugMode){
          trace(STRING);
     }
}

This store was built using the Magento eCommerce script.

The hurtle that I was able to get over was making the facebook calls work from the swf itself. The swf currently has to be on facebook to work properly but I believe I might be able to figure out a way to make it work when the user isn’t on facebook.

This is a funny flash game where you have one minute to find a way to save the drowning boy in the pool. It is a little morbid but it’s really funny and memorable and people like games that surprise them. This was a project that was made with another artist and a musician. Click see more to play the game.

W:Jump
A and D move left and right
S: Go invisible when yellow or drop from ledge when hanging.
J K L or Clicking the screen: Change the color of your body.
SpaceBar: actions for each ability.
R: flip switches and enter doorways