Proof of Concept Notes

Some notes on the original 4k proof of concept that don't apply anymore now that I've moved to a 16k version. For the 4k version I had custom kernels for each scene, which took up a lot more space but let me have fancier graphics effects.


Note: these were captured with the Stella emulator.

The title. Nothing special here besides the asymmetric playfield. The original game has more of a plasma/fire effect on the letters but a gradient will have to do.

The star fissure. I was trying to go for a star effect by having some motion on the ball and turning it off and on in a relatively prime way, but it was hard to get it to look nice and I ran out of cycles in the kernel when I added animation. So for now it's a static effect. I had to play a lot of tricks to get the falling person sprite to fit. Ideally the vertical would scale as well as the horizontal while falling, but again was low on room.

The linking book. I wanted more going on in the link window but again ran out of cycles so all you get is a color change. Playing a lot of tricks here. Using a reflected playfield gave back some cycles, the right side is sprite1, there's a playfield color-change mid screen hid by the sprite0 missile acting as the book spine. Sprite1's missile makes the colorful book binding on the left, with the colors changed mid-screen. All of this and also an animated hand cursor. If only I could get a better version of the linking noise.

The arrival location. I did this last and was low on ROM. Tried to save space using a mirrored playfield which I alter mid-screen, ran into some trouble. Was also learning a lot about how HMOVE works to get the ship's mast to be diagonal down there. I might rethink this one if I can find some time.

I really wanted to have the right side of the spaceship be all black but didn't have enough cycles in the kernel to fit it. I also had to chop off the nose of the rocket which saved a few cycles and a lot of ROM space by having a constant value for playfield 0. Not as happy with this one either.

The clock, I like how this turned out. Using the sprite0 missile for the tree trunk (I do this trick a bit, it's why the pointer color varies from scene to scene). The sprite1 overlay for extra colors isn't perfectly aligned but I thought it gave a nice almost 3-d effect.


Here's a video of the old 4k version 1.0 captured on real hardware:

Back to the Atari 2600 Myst Demake