Dragon Demos

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A collection of demo or work-in-progress (or possibly destined to remain proof-of-concept) Dragon software.

• Nyan Cat
• Horizontal Scrolling
• Line Drawing
• Vertical Scrolling

Nyan Cat

The famous video comes to the Dragon 64!

• nyan-dragon.cas Dragon cassette.
• nyan-dragon.dsk Dragon disk image.
• nyan-coco.cas CoCo cassette.
• nyan-coco.dsk CoCo disk image.
• nyan-dragon.tar.gz source code.

To load the cassette images, attach the appropriate one and type CLOADM. Press Space when prompted. To load from the Dragon disk image, attach it and type RUN"DEMO.BIN". To load from the CoCo disk image, attach it and type LOADM"DEMO":EXEC. 64K required.

The binaries are now compressed with dzip.

The tech stuff: the animation is a 12 frame loop running at 12.5FPS. The music is three channels (one sample, two waveforms w/ arpeg) mixed at 10055Hz (slightly slower on many real Dragon 64s due to adjusted core clock).

Thanks to:

• prguitarman - for the original animated gif
• daniwell-P - for Nyanyanyanyanyanyanya!
• saraj00n - for putting them together and creating a massive hit
• KingYakko - for the MIDI file used here
• Rem - for the mixer core, modified here to play samples
• ? - the intro notes came from this, and I don't know who made it!

Horizontal Scrolling

Horizontally scrolling shooter demo. Technical features:

• 42 bytes per line video mode.
• Smooth horizontal scroll with sprites updated at full PAL screen rate.
• Utilises FAST CPU rate while outside the active area. This avoids display corruption and allows plenty of RAM refresh during each frame.
• Dynamic sprite compilation: over a series of frames, compact sprite data is "compiled" into machine code that draws directly to the screen. This means sprites can be drawn very quickly, while allowing more sprites to be stored in the compact format.

• scroll.dsk disk image.

This disk image is "dual boot": it should work on both the Dragon (using DragonDOS) and the CoCo (RSDOS). To start, in DragonDOS: BOOT or RUN"BOOT". In RSDOS: DOS or LOADM"BOOT".

Keys are W, S, A, D and Enter. P pauses, and within pause mode, Break will restart the demo level. Some number keys adjust options like player speed and firing rate.

Line Drawing

An Asteroids-esque environment demonstrating line drawing. All the vector offsets are precalculated, but line drawing is done properly. Keys A and S allow rotation of the ship, but nothing else works.

• line.bin DragonDOS binary.
• linec.bin CoCo binary (old versions of XRoar will only directly load this type).

Vertical Scrolling

Fast full-height vertical scroll, albeit in a lower resolution. Not very much CPU time left after this, not sure it could be turned into a game really. Keys (in the CoCo keymap only!) are W, S, A, D and Enter.

• vscroll.bin CoCo binary.

Updated 22 Jan 2012