Rebellion on Pern


Centuries ago, your people invaded Pern and defeated the Gah. Surveys showed that the planet was rich in extremely rare minerals so the Ogro (a genetically engineered race) were forcibly brought to Pern to work as miners.

Now the Gah are rebelling and have armed themselves and the Ogro.

Your scanner shows that they appear to be searching for something. Whatever it is your task is to destroy them all as fast as possible.

The Ogro are big and slow so should be easy to deal with but the Gah being faster will be harder.

Armed with the latest trans-plasma rifle are you are ready to hunt them down?


The display shows the view directly in front of you. You can turn left or right by moving the mouse horizontally, the rate of turn increases as the mouse moves away from the centre.

You can only navigate while the mouse is over the display and its position is shown by the four yellow indicators on each side of the display. If the mouse moves off the display the indicators turn red and a large warning appears showing the direction to return the mouse back over the display. Rapid mouse movement makes it very easy to move off the display so be warned. The compass (top-centre) shows the direction you are facing.


You can move forwards or backwards and your current speed is shown in the vertical indicator on the right. You can increase / decrease your speed by holding down the [W] / [S] key respectively. Alternatively, it is possible to automatically adjust your forward speed using the keys [1] to [5] and the [X] key will bring you to a stop.


Use the mouse to centre the rifle over an enemy then either click the mouse button or press the [Enter] key to fire a plasma sphere. After firing it takes a few moments to recharge the rifle, a solid yellow ring indicates a full charge. You can use the scanner to find the enemy, it is activated by pressing the [E] or [D] keys. You cannot fire the rifle while the scanner is active.


The scanner will detect both Gah and Ogro and show their position relative to your current position. The scanner has better distance resolution for enemies close to you (near zone) but distant enemies can still be seen in the far zone. The counter shows how many enemies are left. Pressing the [E] or [D] keys or clicking the mouse button will close the scanner and reactivate the rifle.

Game play

There are 4 Gah and 8 Ogro in your sector, if you can defeat them all in under 4.5 minutes then you are doing very well but any time under 6 minutes would be considered good.

When starting the first game the animation might be a little jerky as the terrain data is passed to the graphics card, if this is a problem start a new game by pressing the [N] key. This will take you back to the user guide screen ready for the next game.

To get the computer to hunt down and defeat the enemies for you, hit the [M] key. This key will swicth you between normal and auto-pkay on / off.

The game play can be paused / resumed with the [P] key.


Component Source Description
Framework P5.js is an excellent Javascript framework that can be used to create a wide variety of graphic applications, including games. Although it lacks the sophistication and power of some 3D engines its simplicity makes it easy to learn and use.
Simplex noise implementation A fast implementation of simplex noise by Jonas Wagner. I used this implementation as part of the code to create 2D tileable height maps for the terrain.
3D models Various Each animation comprises of two models, the creature and its weapon. A number of people were involved in creating the 3D models and the skins. To give them full credit I have included links to the original text files they provided with the model data. Click on Gah or Ogro to read about that creature.
The only changes I made were to edit the animation state names so they matched for both Gah and Ogro, and to correct a glitch in one of the Gah death sequences.
Music / sound effects To get details about the sound and its creator search the site using its id number
514178 : opening music
610679 : game over music
231261 : birds singing
433725 : running footsteps
I modified the last sound trying to make it deeper using Audacity but without a lot of success. As to the explosion sound I have had that so long I have no idea of its origin.