July 2007 - XNA Game
Encroach


Features
  • Simple and addictive gameplay
  • 1-4 players
  • Runs on both XBox 360 and PC
  • Entered into the Microsoft Dream Build Play competition
  • Heavy use of custom shaders and post-processing techniques
Summary
Encroach blends action and puzzle elements to provide an addictive gameplay experience.

Central to Encroach are the four colours found on the XBox 360 gamepad controllers - red, green, blue and yellow. The concept is very simple: players shoot bullets of any of the four colours by pressing the corresponding coloured buttons on the gamepad. The players are all located on a small central island, and encroaching upon them are a number of circle segments which can only be destroyed by being shot with the matching colour. Shooting them with the wrong colour incurs a penalty. The game ends when the players fail to destroy a circle segment before it reaches their central island.

Encroach can be played as a single player experience, or multiplayer with 2-4 players. Two and three player modes offer an interesting blend of competitive and (then when things start really start getting going!) collaborative gameplay. Four player mode provides a unique Encroach experience as each player is locked to a single colour, forcing everybody to work together to survive.


Download
Freeware
Free to download and use for non-commercial use.

Technical Details

Encroach was designed and written in our spare time over a 3 week period. Originally it was meant to be one of a collection of mini-games revolving around a central theme, but we decided it was best to focus on finishing a single game to a higher standard rather than spread ourselves too thin. We hope to continue implementing the other mini-games in the future.

The circular segments that feature in the game are generated using a custom pixel shader. As well as drawing a pixel-accurate ring to any radius, the shader also anti-aliases the edges and applies slight rounding to the corners of the segments - we hate jaggies :). The game runs at a native resolution of 1024x768. An 8-pass Kawase blur is used to create the glow effect.

We needed a good solution to make the text more readable on a background of varying colours. The XNA framework helpfully provides a tool for bitmap font generation, but it is quite basic and has no support for things like outlining. We solved this by rendering the text to a separate texture, running a dilate filter over it several times and then using this slightly fatter text as an alpha channel for alpha blending the text into the final render. This effectively provides a black outline of customisable width to all the text. A bit expensive perhaps, but it looks nice and in image-space there are so many possibilities. We also use an erode filter image effect to make the circle segments disappear when they have been shot.

Encroach was written in C# and uses the XNA framework. We used Subversion for source control and Retrospectiva for project management and bug tracking.


Video

Short video of the game in action. Download high-quality version (9.83 MB XVid)


Screenshots

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