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Blogs

Shelter in place!

July 8, 2020 Retro Ports

The shields are now rendered in the correct location on the screen. As planned, the code now buffers the complete 512-byte area of the screen containing the shields. So whilst the rendering into the buffer is now more complicated, the save/restore is a simple block copy. This is in contrast …

Blogs

Shielding you from the ugly truth

July 1, 2020 Retro Ports

I’ve rotated the shields and have them rendered on the screen… Shield locations are only approximate at this point … but, and it’s a pretty big but at this point, not accurately. The locations are only approximate atm, off by progressively a few (more) pixels for each shield left-to-right. But …

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Blogs

Less magic, more explosions!

June 10, 2020 Retro Ports

Not much time to work on it as I have a sneaking suspicion that getting Space Inavders working on the CoCo3 is pretty low on my employer’s priority list.Fixed the player explosion, UFO explosion and the UFO score when hit.A number of ‘magic numbers’ in the disassembly have been fixed, …

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Blogs

Things are about to explode!

June 8, 2020 Retro Ports

Two very brief sessions over the last few days.Player lasers and alien explosions are all-but-fixed now. I’ve realised that I need to go back and review all the reference points used for the rotation again. But it’s something I’ll leave until all the rendering routines at least look correct, even …

Blogs

This is Da bomb!!!

June 5, 2020 Retro Ports

Unexpectedly got a bit more time tonight to work on Space Invaders.Started to look at the invader bomb rendering code. The routine that renders a bomb also checks for collision with other objects; namely shields and player laser base. I decided to concentrate on the rendering for now and worry …

Blogs

Unidentified Fixed Object!

June 5, 2020 Retro Ports

Not a lot of time to work on it today so a quick update – UFO fixed!The UFO sprite has 4 blank pixels on each side in order to self-erase when flying across the top of the screen, for a total of 24 pixels across. However, when displayed in the …

Blogs

Being a bit more specific

June 4, 2020 Retro Ports

Another session tonight and very good progress. Coding object-specific rendering routines is definitely the way to go.First cab off the rank was the player base. Once I had that sorted, to render the invader it was simply a case of writing a small loop to erase the area above, then branch …

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Blogs

Vertical monitors and self-erasing sprites

June 3, 2020 Retro Ports

In search of low-hanging fruit I decided to fix the logic for detecting the edges of the screen so that the invaders reverse direction at the right point.I decided the quickest and most reliable process was trial-and-error. I ultimately ended up with the right magic numbers in the code; whether …

Blogs

Leaving behind footsteps

June 2, 2020 Retro Ports

As usual, it’s a case of two steps forward, one step backwards.I’ve ‘improved’ the sprite rendering but in the process have discovered a complication that is a direct result of the rotation.Ordinarily, the invaders march ‘across’ the screen on a vertical monitor, which means they march ‘down’ 2 lines in …

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Blogs

Addressing some issues

June 1, 2020 Retro Ports

I think I’ve just doubled the number of posts from last year in just 2 days this year!?!At lunchtime today I continued where I left off last night. A few red herrings along the way but I’ve managed to identify a couple of issues that explain the crashes, and even …