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I'm making a strategy game for Android. The main focus is two player local turn-based game. The setting is mythological, with Greek Mythology and some other creatures like Dragons, Unicorns, etc.

It will revolve around Cards, but it is not a collectible card game. Rather, both players can choose cards from a fixed deck and they can use any of the cards at any time during combat. Here's one of the cards:

(http://bigosaur.com/blog/images/medusa400.jpg)

It will be optimized for tablets, I got Nexus 10 to test  :) But it will also work on phones. I plan to support resolutions from 800x480 to 2560x1600.

The game will be completely free to play, without IAP. I might put some ads inside. This is part of LudumDare October challenge, so I plan to make it complete by the end of the month.

I'm using letterboxing with filler background to support all the possible resolutions. Here's the main menu:

(http://bigosaur.com/blog/images/2560gos.png)

On my blog I wrote a couple of useful articles for Android developers. Mostly the stuff I can use later as a reference when I make another Android game:

1. Supporting multiple screen resolutions on Android
   http://bigosaur.com/blog/31-android-resolutions-definite-answer (http://bigosaur.com/blog/31-android-resolutions-definite-answer)

2. Using ImageMagick to scale images for multiple resolutions automatically
http://bigosaur.com/blog/33-android-imagemagic-script-scale (http://bigosaur.com/blog/33-android-imagemagic-script-scale)

2. Activating Immersive Mode on KitKat and newer Androids
http://bigosaur.com/blog/32-handle-immersive-kitkat (http://bigosaur.com/blog/32-handle-immersive-kitkat)

I'm still learning how to draw well, and I'll make all the artifacts images. But for units, I needed some good artists to make nice pictures. I searched the fiverr.com and found some really good ones. Here are some pictures I commisioned for this game:

(http://bigosaur.com/blog/images/270dragon.jpg)

Most artists on Fiverr are only good with a particular style, so make sure you look at their portfolio before ordering. For example, an artist from South Africa with username seatongrey (https://www.fiverr.com/seatongrey) has a great style that would fit Underworld units in Gods of Sparta. But I wouldn't use him for Human faction. He made the Dragon above, and here's the Hades:

(http://bigosaur.com/blog/images/270hades.jpg)

For Human units, I hired glass84 (http://fiverr.com/glass84/paint-in-photoshop) and johannan (http://fiverr.com/johannan). Here's Achilles from glass84:

(http://bigosaur.com/blog/images/270achilles.jpg)

The turnaround is usually a couple of days. You can see the average in the artist's profile. Now, be prepared that some artists might be busy and won't get back to you quickly (or ever). If that happens, just cancel the gig and hire another one.

Be prepared that some designs might fail. For Olympus units I had to combine different artists. flannery (http://fiverr.com/flannery) is good with horses, so I got Pegasus and Unicorn:

(http://bigosaur.com/blog/images/270unicorn.jpg)

Here's how I have drawn the ring artifact for my game in Inkscape. I hope it helps others if they need to create similar art.

On of the artifacts in my game is the mythical Ring of Gyges. I decided to improve my graphics skills and learn Inkscape better. Rings and other metal surfaces are rather simple to draw, you just need to combine proper gradients.

(http://bigosaur.com/blog/images/inkscape_ring.png)

I started with basic eclipse, duplicated the shape multiple times and then created unions and intersections needed to assemble the ring. I used a brown-gold-white-gold-brown gradient (it's easy to make a custom gradient like this in Inkscape). To get the proper gradient (straightforward or reverse) I put a real ring on my desk and watched the colors.

This is the basic ring. But lets make it look really good. First I rotated it about 180 degrees and then added a gem to it:

(http://bigosaur.com/blog/images/inkscape_ring_final.png)

As you can see the gem has multiple layers. On the bottom we have a black circle with white border. Border is not the same everywhere, it has a gray-white gradient stretching from left to right. Outside it, there's another border, with black-to-transparent gradient. This is used to create a 3D effect on the ring's metal surface. Over that, we have a half-circle with another gradient. This time the gradient is radial, extending from the bottom-left corner which has a white point. That point looks like a point where the light enters the gem. This is the base. Now we will add color. You can pick any color. I choose blue.

First, we create the dark blue overlay (one the the right in the image above). Note that is also has a slight gradient going from left to right. The light blue layer on the top is used to complement the bottom-left white point in the black and white base. As the light enters in the bottom-left corner it goes through the gem and exits in it's top-right part. There is no sharp point there, although you could put one if you want to achieve a different effect.

Finally, here's the artifact's card in my Gods of Sparta game:

(http://bigosaur.com/blog/images/ring_of_gyges.png)

Copied from my blog: http://bigosaur.com/blog/36-creating-ring-inkscape (http://bigosaur.com/blog/36-creating-ring-inkscape)

For card animations in Gods of Sparta I'm using the largest card graphics all around. The cards get scaled and rotated as they move. To rotate the image around it's center, you need to setOrigin to (width/2, height/2). However, the origin is also used for scaling, so if you scale the image it will no longer stay at the same (x,y) position you set with setPosition.

(http://bigosaur.com/blog/images/libgdx-scale-origin-setposition.png)

To get the scaled image in some particular position, you need to offset the coordinates. See the image below for the exact math:

We want to position the scaled image to (60,70), but since it has setOrigin, it shows up in a different spot. To place it properly, we need to move it half of the difference between full and scaled image.

Now that we know how it works, it all makes sense. I hope this saves other developers some time.

I know players hate reading complex rules, so I tried to make a screen that would explain how the cards work without getting too complicated. Here are the basic rules:

(http://bigosaur.com/blog/images/gos-rules.jpg)

At the start of each game, the players are presented with a deck of 20 cards and they take turns picking one by one until each has 10 in their hand. After that the battle starts.

(http://bigosaur.com/blog/images/gos-pickcard.jpg)

When the first player picks the card, all the other cards rotate 180 degrees to face the player sitting across. It's a two-place local duel game.

If got a lot done in the past two days. The main battle mechanics work. You can place and move units, and attack. There is still no attack animation. As you can see on the screenshot, some units are turned upside-down. This is because it's a two player game. The idea is that you put the phone/tablet down and sit across each other and play.

(http://bigosaur.com/blog/images/gos-move.jpg)

Flying units like dragons can reach any field, while others have to move one step at the time. Each turn, a player can move and attack, or attack only. Once you attack, it's the other player's turn.

I'm currently drawing some attack icons. When you select your unit in the field, those circles would rotate over the adjacent enemies and you can pick which one to attack.

(http://bigosaur.com/blog/images/attack_circles.png)

Depending on the attacker, a different circle would be used. Olympus units would get a blue round one. Humans get the yellow square (at least I tried to make it resemble a cross). Underworld units have the hexagram. I drew all these in Inkscape.

I decided that I have to change the screen orientation mid-project. I'm switching to Landscape orientation. Here are the reasons:

• attack graphics looks odd upside down
• I want to provide hints how damage is calculated, awkward since all the enemy cards are upside down.
• Thumbnails used to pick units from your deck are too small on phones.
• YouTube videos are landscape.
• Desktop version of the game (if I ever release any) can use larger resolution.
• I can test larger resolutions on my monitor instead of having to run it on the Android devices.
• Players will sit next to each other, so they won't have to put the device down on a table to play. You can play it with a friend in a bus or on a train.
• Much more available screen space for unit stack and enough space for additional user interface. See how everything is crammed currently and a lot of space is wasted sideways:

   

(http://bigosaur.com/blog/images/gos-dragonsfly.jpg)

There are some cons:

• I have to redraw some of the graphics
• I now need horizontally flipped unit graphics which will almost double the memory consumption of the game (I cannot simply flip the whole card, as it contains pregenerated text as well)
• The drafting screen cannot use the rotations to indicate current player

   
To conclude: unless the game is meant to be played like flappy bird (using the same hand that holds the phone and having only one command: “tap anywhere”) use the LANDSCAPE orientation.

As I switched to landscape (http://bigosaur.com/blog/40-use-landscape-android-game) mode, I started to create mirror-flipped images of unit cards using the -flop option in ImageMagic in one of the card-generating steps. As the script rolled on for some time, it hit me that this would increase the amount of graphics a lot. I got worried about the size of the final .apk file. First time since I started the project I decided to check.

I created a package containing only the lowest (800x480) and highest (2560x1600) resolution images. It's 106MB!

I need to add 4 intermediate resolutions, so I'm looking at 300+ MB for the final .apk. I searched the docs and found that the limit is 50MB and rest has to be provided as a separate package. Or, you can distribute two different .apk files. I didn't like any of those. I hate when you download an Android game, and then you have to wait for it to download hundreds of megabytes more. I needed a new approach.

I searched the Internet. Most advices are about packing your code using compressor/obfuscator programs. But the gains are really negligible. Then one thing caught my eye: using JPEG for textures. I'm using TextureAtlas to pack everything automatically, but I could separate the images with and those without transparent areas and pack them separately as PNG or JPG.

The problem is that 90% or the graphics need transparency. In this particular case the main problem are the card images, which have rounded corners. And then I got this great idea: separate the card image into frame and contents. There are only four card types in the game (one for each faction and gold one for the items), and all cards of the same type share the same frame. The inside of the card is different for each one, but it does not require transparency. Instead of packing 126 cards into PNG texture, I would pack 126 cards into JPG texture plus 4 frames into PNG.

(http://bigosaur.com/blog/images/framepluscontent.png)

As I tried this, I got some weird clipping artifacts in the JPG texture, probably because I turned off (http://bigosaur.com/blog/33-android-imagemagic-script-scale) the 2-pixel padding. So, instead of pixel precise cropping, I increased part of the graphics that gets copied to JPG so that there is some overlap. When staging the images, make sure the jpg one is drawn first and PNG frame over it. The part that overlays will covers the bad edge pixels.

BTW, by “staging” I mean placing the Images into libGDX Stage. To make the code simpler, I created a nice CardImage class (descended from Group) to handle drawing transparently. This Group contains the center of the card from JPG texture and then positions the frame from PNG texture over that.

This saved A LOT, but I got so concerned about the size that I wanted to do something about flipping as well. I researched if I could only flip a part of the image. It's possible using AtlasRegion.flip() function. But I also had the problem that I didn't want to flip the whole image. The textual part should remain the same and only the unit graphics should be mirrored. To do this, after calling flip(true,false) I used setRegionY and setRegionHeight to reduce the flipped region size. Using the flipped region I created another Image and added it to the CardImage group. At runtime, I simply show or hide this image when I need to unit to face left or right.

Result

New .apk file with the same content is now only 12MB. A 88% save. Once I add all the other resolutions, I estimate the final .apk to be about 40MB if all goes as planned. Compare this with 300MB+ I expected at the beginning.

TL;DR Summary

Beside all the other advice you might find on the web (compressing the code, etc.), add these three:

• use JPG wherever possible
• if you use PNG only for semi-transparent border, cut the image into frame + content. Store the frame in PNG and content in JPG Of course, if your frame is not reusable on multiple images and has complex colors this my have the opposite effect. However, there's a solution to that as well: cut the frame into four pieces (left,right,up,down) and assemble it at runtime. No more empty space in the middle of the frame in PNG.
• If you have images that are flipped or rotated, store only the original and flip/rotate at runtime.

I finished conversion to landscape mode and implemented the attack icons and animations. For most attacks the cards just move and shake a little bit. Ranged units have special animations, Zeus fires thunderbolts and Catapult throws rocks at enemies. I added the damage numbers to attack icons and it's now visible which type of attack deals the most damage.

(http://bigosaur.com/blog/images/gos-energy-attack-defense-modifiers.png)

I also created some nice icons for unit Energy (heart) and also Attack (sword) and Defense (shield). Those show up when the default unit values are modified (by artifact or an ally that stands next to them). This makes the game fluid to play, as you don't have to keep do the calculations manually all the time.

What's left to do: Turn indicator graphics, Sound effects, Music (I'm going to get help from a musician), AdMob integration. Initially the game was supposed to be only a two-player game, but now I'm thinking about single player mode as well. Writing good AI for this strategy might get complicated, but it's worth a shot. There's still enough time before the end of October.

Final release is ready:

Download:
https://play.google.com/store/apps/details?id=com.bigosaur.gos.android (https://play.google.com/store/apps/details?id=com.bigosaur.gos.android)

YouTube video:
https://www.youtube.com/watch?v=IXgOGmsQtKQ (https://www.youtube.com/watch?v=IXgOGmsQtKQ)