Fourth Week Mobile Game Progress Update

Another week, another progress update. As usual you can check out the progress above (use the arrow keys to move and jump).

This week has mostly been about all the remaining “bits’n’bobs” that go into a game. That includes level progression, scoring, level and stage unlocking, persistence, settings, audio, pause and resuming, player death, fonts and a whole host of other small things.

Moh my artist partner on this project arrived back from his week holiday this week and since back he has made incredible progress getting all the menu screens and the majority of the graphics for the first stage of levels in. I really love the bright cartoony style he has gone for on the menus, the style really works on mobile too. Looks really professional for less than a weeks worth of work (only evenings dont forget).

I have also spent some time sourcing and putting in the rudiments of music and sound effects. The music theme for the game has been supplied by another colleague from Playdemic, Jake Rigby. Before Jake got into game programming he used to make music and audio effects for games (infact he provided some of the audio for my previous flash games) and he was very kind to provide me one of his tracks he made a while back for the project. The sound effects in the game are temporary at the moment, I hope to improve them this week 🙂

I have also been working hard on trying to get as many levels in as I can. As mentioned previously the idea is to have 30 levels split over three ‘stages’ each stage will have its own theme and general style of levels. So far I have made the first 10 levels in:

As mentioned in my last update I noticed that people were having trouble understanding how to play the game with the world rotating. To combat that I decided that the first few levels the world were going to be static, doing so should reduce some complexities with the control system. Well I have extended that “few levels” to now mean that the entirety of the first stage doesn’t auto-rotate.

What I have done instead is to re purpose some tile types I had originally planned. You are introduced to the first of these new tile types on level 3 of the game. I think it brings that added sense of dimension to the game, making it more than “just a platformer”. Play it above and see what I mean, or check out the video I have made of it working on the devices:

Incredibly the game actually runs at a very acceptable 30FPS on my iPhone 3G! Eat your heart out Adobe AIR!

Good level design really is a talent that I admire as I im absolutely terrible at it. It takes alot of time, patience and testing none of which I have in abundance. It is however critical to making this game fun to play so unfortunately I will be concentrating on level design the most of this week. I would love to hear about any feedback you have on the levels, whether they are too hard, too easy, whether the progression is right. It would be a massive help to me and is only something I can get a rough idea by testing myself, it needs others to play test it 🙂

With that in mind, onto time-scales. In my first post on this project I declared that I was going to finish this game within three weeks. I then extended it by a week due to my artist being out of action for a week. I am now going to extend it by one final week. I am starting to feel really proud of this little game and I think it would be a shame not to put one final weeks worth of polish in before calling it complete. So although I can no longer call it a “three week game” I can be proud to call it “my first mobile game” 😉

3 Weeks of Progress on a Mobile Game

As usual you can have a play with the game in its current form above. (Up to jump, left and right to control the player).

The first new thing to notice are there are now menus, yey! Incredibly poor, made by a toddler, looking menus, but menus nonetheless. My artist and collaborator on this project, Moh, has been away for the last week so the game has had to suffer at the hands of my terrible programmer art. Now that he is back however, he will be whipping the visuals into shape.

Again this week I have had far less time to work on the project that I was hoping for (damn real life). With the little time I have afforded myself, I mostly concentrated on menus, resolutions, DPIs and aspect rations. These topics are the rather unglamorous side of mobile programming but are a necessary part of writing a game for multiple devices.

First a note on my testing environment and devices:

PC (flash) – 1024×683 @ 72 DPI
iPad3 – 2024×1536 @ 264 DPI
iPhone 4 – 960×640 @ 326 DPI
iPhone 3G – 480×320 @ 153 DPI

(I currently don’t have access to an android device but I hope to test on it soon.)

As you can see there is a rather large variation in resolutions and Dots Per square Inch (DPI). There is also two different aspect ratio’s there 4:3 for the iPad and 3:2 for iPhone. The iPhone 3GS is the same aspect ratio but half the resolution as the iPhone 4 and the iPhone 4S is the same aspect and DPI as the iPhone 4. The iPad 2 is half the resolution of the iPad 3 but has the same aspect ratio.

Basically all this equates into a few days of headaches while I try to wrap my brain around how to handle this mess. My solution to this conundrum is set my default target to the iPhone aspect ratio of 3:2 as it is more restrictive in the Y direction than the 4:3 ratio of the iPads. If I can build menus that work in 3:2 then they should look okay (if a little bit more spaced out) in 4:3.

To handle the various resolutions within an aspect ratio I then need to provide various versions of the assets that would roughly take up the same amount of screen space at that resolution. So for example if the screen is 1000px wide for example and the title for a menu is 800px wide when I design it on my PC, I would then need to provide a 1600px wide title image when running on a screen 2000px wide.

So the question is now how to provide these various sizes of my title? Well I could make a PNG for my title 800px wide then when I need one 1600px wide I just scale it up by two. The problem with this as anyone who has played around in Photoshop will know is that you will end up with a blurry up-scaled image. The other solution is to start at the other end with the highest quality 1600px then scale it down when you need one 800px wide, the problem with this is that you are wasting a whole load of memory by supplying and loading an image twice the size of whats required. The third method is to provide a different size for every single resolution required, this is not ideal as it would take alot of time to make all these PNGs and there are a great many device resolutions out there.

Haxe and NME however give me an alternative solution. Using the SWF library I am able to design my menus in Flash then at runtime pull out the vector graphic and scale it to the required size to display on screen. What this means is that I only need supply a single resolution of an asset in flash then it is scaled up as a vector and looks great no matter the resolution.

So to work out the correct size for the various parts of the menus initially I created a few “mock screens” in flash and laid out the various parts in the mocks:

By designing the mocks to 960×640 (3:2) I need only then at runtime divide the screen width by 960 to work out the correct scale for the game. Simples!

Well not quite as simples at that. There were a coupple of issues. Firstly the vector rendering performance of NME on mobile is pretty poor. To get around this problem you must pre-raster your vector to a Bitmap first. This should be fairly normal to anyone having worked with Blitting engines in AS3 before. This step however raised another issue.

I noticed it was taking a long time to raster the background for my menus to a bitmap. I did a few experiments and posted the question on the NME mailing list. It turns out that NME currently doesnt handle Radial gradients too well, also performance is generally poor when building in debug mode on iOS. With both this issues rectified however the performance was alot better. There is still a small lag between different menus when on iOS but its acceptable for now.

There also appears to be another issue regarding TextFields on iOS. It appears as if the text is being cut off half way. I have also posted about this issue on the mailing list and am awaiting a reply. My solution for now is to provide a background behind my text set to alpha 0, this forces the width and hight to be correct:

Well with that boring stuff out of the way onto the changes in the game itself.

As mentioned previously the gameplay changes have been fairly minimal. I have made some small changes to how the player is controlled to make it more fun. You can no longer scale vertical cliffs and jumping has been modified. The largest gameplay change has been to how the player is eased into the game.

After watching people play the game on the iPhone and iPad I noticed that alot of the time people didnt seem to understand how to control the player. They assumed the game worked like one of those “move a ball around a maze” type games. So understandably they kept turning the device on its side in an attempt to make the player “go up”. With the world constantly rotating too, the person was trying to keep the world level, so they kept twisting the device in odd directions to keep it level. This problem is difficult to explain if you haven’t tried it out on a device for yourself.

Once you understand whats going on however (the world is rotating, you tap to jump and tilt to move the player) it all becomes alot more clear and you can play the game normally. So with that in mind I have decided that the first few levels the world will not rotate. I hope this will ease a player into the control system a little better rather than just throwing them at a strange control system in a continually rotating world. Fingers crossed this will do the trick.

So that’s that for this week. This week we hope to get as much of the art work in as possible. Hopefully menu systems, and the various bits of artwork for the stages will all go in this week. In addition I want to get audio and testing on Android in. Alot to cover in very little time!

2-Weeks In.. Mobile Game Progress Report

I’m now two weeks into my original 3-week-deadline mobile game project. You can checkout the progress thus far by playing the game above (‘up’ to jump, ‘left’ and ‘right’ to control the player).

As you can see there has been some progress since my last update a week ago. I was hoping to have gotten a little further by this point but my personal life has been somewhat hectic the past week reducing the amount of game-development time to a few measly hours. In the few hours we have had, we have managed to get a general story / theme for the game and the rudiments of for the first ‘stage’.

So the story is that our furry marsupial protagonist has ambitions of breaking free of his earth-bound cage to become the first hamster in space. The game is about his adventure to realise this dream.

The plan is to break the game levels in into ‘stages’ like other mobile puzzle games such as cut the rope or angry birds:

Each stage will have its own theme, giving the player a refreshed experience per stage. The first of these is going to be set within the cage itself so the tileset and background should hopefully represent that.

The bulk of my work this week however has been spent trying to get the game controls working just right. It needs to be fun to play, not too frustrating but not too easy. This is easier said than done. Im not sure its quite there yet, but play the game above and let me know what you think, im keen to hear your opinion.

During the last week I also ran into a few nasty issues with the physics which I thought I had nailed in the previous post. The problem was that the issue only occurs at low frame rates, this was really noticeable in the last post when I tried the game out on my iPhone 3G, the player was extremely jerky and unplayable.

To test the problem quickly (without needing to do an iPhone build every time) I used the handy “fps” attribute in the NME .nmml file. Setting the fps to 60 then having the player jump then setting the fps to 10 and having the player do the same jump there was a noticeable problem. On the 10fps build the player couldn’t jump anywhere nearly as high as in the 60fps build.

I knew that the reason for this problem lay somewhere in my update function in my Player class. My usual method of running update loops is to work out the time between two frames (delta) in milliseconds, pass that into the update loop for a game object then have the game modulate its update based on that delta. So as a very simple example:

[codesyntax lang=”actionscript3″ lines=”normal”]

class Player
{
	public var position : Vector2;
	public var velocity : Vector2;
	
	...
	
	public function update(delta:Int)
	{
		position.x += velocity.x * delta;
		position.y += velocity.y * delta;	
	}
	
	...
	
}

[/codesyntax]

This is pretty standard stuff and should be familiar to any game programmer. In theory it shouldn’t matter what frame rate the game is running at, the player movement should be consistent because the velocity is being modulated by the time between the previous frame and now.

The code for the Player class however is quite abit more complicated than the simple example given above and something in the logic was causing problems. I had my suspicions but no matter what I tweaked or changed I couldn’t track it down.

I had however read of a different technique documented by deWiTTERS that involved a different way of writing your game loop that didnt take into account of frame delta but was still able to provide a consistent gameplay at differing framerates.

I wont detail the process here as dewitter explains it very well in his post. The result is a greatly simplified update loop for my Player by removing all the delta time factors. My resulting update loop now looks like:

[codesyntax lang=”actionscript3″ lines=”normal”]

class Game
{
	public static var TICKS_PER_SECOND : Float = 50;
    public static var SKIP_TICKS : Float = 1000 / TICKS_PER_SECOND;
    public static var MAX_FRAMESKIP : Float = 10;

	...

	private function onEnterFrame(e:Event):Void 
	{
		var loops : Int = 0;
        while( Lib.getTimer() > nextFrameTime && loops < MAX_FRAMESKIP) {
            update();
            nextFrameTime += SKIP_TICKS;
            loops++;
        }
        render();
	}	
	
	private function update() 
	{
		Ctrl.instance.update();
		objects.update();
		camera.update();
		bg.update();
	}
	
	private function render() 
	{
		tiles.render();
	}
	
	...
	
}

[/codesyntax]

The result of doing this is that the game now runs consistently at 60fps or 10fps. I haven't tried it out on my 3G yet but I have high hopes for the technique.

The moral of that story, if you bang your head against a problem for a while, just take a breath, think outside the box and attack it from a different angle 😉

Well that's about it for this week. The original intention was that is was going to be my last week of working on this game. (Un)fortunately my artist partner has gone on holiday this week so he is unable to work on the game, the result being I have given us an extra week to complete the game, yey! 🙂

Oh BTW, the title for the game is hidden in the demo above, see if you can work out what it is 😉