Genre: Arcade      Creation Date: June 2015      Language: 6809 Assembly Language    System: Tandy Color Computer 1, 2 and 3


I created the original Neutroid back  in March 1983. It was my second complete assembly language game for my first computer, the TRS-80 Model 1. Neutroid featured fast graphics, impressive sound and frenetic action. It was a great arcade game that pushed the capabilities of the TRS-80 Model 1. At the time, I thought I had a real winner on my hands but as fate would have it, it didn't exactly set the market on fire.

Later in 1984, I switched across to the Tandy Color Computer with color and high resolution graphics. But it was not my ideal choice. There were several other systems on the market with better graphics and sound capabilties for much the same price.

But the Color Computer had two things in it's favour that interested me. Firstly was the excellent Motorola 6809 CPU, clearly the leader of the 8 bit CPU's at the time. Secondly, the Color Computer had a wide distribution network via the 700 Tandy Electronics stores across Australia at the time. Although the Color Computer's Motorola 6847 video chip did not impress me, these other two factors did and I decided to take up the challenge to create software which would push the machine's limitations to a new level.

With an idea to create a game using the underutilized 8 color semigraphics modes, I settled on recreating Neutroid for the Color Computer and created Neutroid 2 in October 1984. This was my first assembly language commercial game for the Color Computer.

As before, I thought I had the ultimate killer arcade game for the Color Computer. As before, it was a flop... an even bigger failure than the original TRS-80 Model 1 version. I was ready to throw in the towel but perservered and later released Donut Dilemma which went on to become my most successful Color Computer game being sold in every Tandy Electronics store in Australia.

So what went wrong with Neutroid 2? It had 8 color graphics, fantastic sound and fast arcade action... all the important ingrediants required by a blockbuster arcade game.

People just didn't get it!

Neutroid was too abstract for people to understand. The atomic theme of the game seemed to be too complex for people to comprehend. There was a preference for games with a character or familiar scenario. Nuclear particles moving on a grid was just too alien.

It was also a very hard game requiring rapid reflex decisions, the ability to track several objects at a time and was too difficult to control with the keyboard arrow keys.

And another problem...

There was another problem which surfaced a few years later.

When the Color Computer 3 was released in 1986, it didn't support the semigraphics modes. Over time, it was discovered that in actual fact it did... at least most of it. All the semigraphics modes could be activated with the Color Computer 3's GIME with the addition of an extra POKE. What it didn't do though was to include the ability to display text characters (ASCII 0 - 127). Only the text mode graphics (ASCII 128 - 255) could be displayed. Most programs using semigraphics would display the score in text characters and this didn't work on a Color Computer 3. Neutroid 2 was no different so although Neutroid 2 could be made to work, the player had no idea of his score during play and any text prompts were invisible.

Although I had moved on from Neutroid into other more familier game styles, Neutroid's failure to capture any excitement always bothered me and I have always felt there were some things I could have improved to make the game more acceptable.

Neutroid returns!

Back in May 2015, the thought came to me to finally resurrect Neutroid 2 and fix the areas that have been bothering me for so long. I still had the assembly language source code and all the graphic and sound media files archived on my PC hard drive.

Two months later and Neutroid 2.015 is complete. Why the name 2.015? Because the update to Neutroid 2 was done in 2015!

Below is a list of changes I did to Neutroid 2. Apart from these, the code is much the same. My goal wasn't to rewrite Neutroid 2 but to make some improvements, adjust the gameplay to make it easier and fix it for Color Computer 3 compatibility.


The new title page

The improved high score page


NEUTROID 2.015 updates


Removal of ASCII 0-127 text and replaced with ASCII 128-256 graphics

The score display was rewritten and replaced with a semigraphics version. Several text prompts were also removed/replaced. The game itself now functions completely in semigraphics and compatible with all versions of the Color Computer including the Color Computer 3. Minimum of 16K RAM required as before.

Removal of keyboard control system and replaced with joystick control system

The original Neutroid 2 used the four arrow keys for control. This was the same as for the TRS-80 Model 1 version. The Color Computer 1 and 2 arrow keys were positioned at opposite ends of the keyboard which made for a comfortable posture. The Color Computer 3 moved the arrow keys in a diamond cluster and created a cramped posture which made it almost impossible to control the Neutroid and led to much finger entanglement... made even worst at my older age.  :)

I highly recommend Tandy's deluxe self-centering joystick. The original free-floating black joysticks are a horror to use and will drive you into insanity. Be aware that Neutroid 2.015 is a high octane joystick destroying game.  :)

Graphics update

The Protroid emittors, Grid Chargers and the display bars graphics (Vault Temperature and Neutroid Energy) have been given a slight facelift. The display bars in particular have been made easier to read and interprete at a glance. During the pace of the gameplay, looking at these displays can be a distraction so they have been made easier and clearer to read. These are critical to monitor closely as you progress into the higher and more demanding grids.

New Title Page and improved High Score page

The Title Page has been jazzed up a bit and the Famous Scientists high score page has an improved light chaser effect. These are only cosmetic but I always thought the originals were kinda drab.

Level progression adjusted

Neutroid 2 was always a hard game. I designed it for the arcade andrenalin junkie but the level progression was too hard. I have adjusted the progression to a setting that I am happy with. Some will still say it's still too hard and will have difficulty getting past the first level but that is a sign that you're not playing it right. Once you work out a few patterns and strategies, the first two levels are moderately easy.

My hands are not as dextrous as they were 30 years ago but now with joystick control incorporated, I can get through 4 levels consistently... then it starts getting insane!

Improved documentation

I developed a new set of instructions to more clearly convey the game concept. I reduced the text of the original and incorporated a screenshot, pointing out what and where everything is.

There is also a YouTube video guide on how to complete Grid 1 (see link below).



Game Screen

Download Game


Download Instructions


YouTube Video


Click on the link above to see a demonstration video of how I complete Grid 1. Grid 1 is the slowest and easiest level. You can see the repeating pattern I use to collect the Protroids. My emphasis is in collecting Protroids rather than avoiding Antitroids. I keep track of how many Antitroid collisions I sustain keeping an eye on my energy bar. When this goes too low, I collect an orange Protroid to give me a few seconds of re-energization and chase Antitroids.