Scrolling viewport

I need to scroll the objects as the stunt rider jumps the buses in order to allow a reasonable number of buses to be jumped. the original Atari arcade machine had 28 buses. I did some test of what this would look like and now I’ve started building the first iteration of the framework that will enable a scrolling viewport.

The system is relatively simple and requires using a double word (16 bits) to represent the location of all sprites and objects. this gives a playfield of 65536 positions. An associated viewport position is also represented using the same 16 bit format. It’s actually quite trivial to check to see if an object is withing the current viewport region as the width of the viewport spans a byte (0-255 points).

It’s quite an interesting effect and allows a lot of possibilities. There is a cost associated with this work but it allows quite complex scenes to be developed with minimal hackery.

I now need to finished the manager that has been partly built to enable this little demo, this will then enable me to finish work on the logic and jumping mechanics.

VecFever setup

Managed to actually play with the VecFever this weekend. Gotta say it’s an impressive piece of kit, drag and drop binary copying if that’s your bag.

But this really comes into it’s own in developer mode, live linked to the PC and VIDE development environment. After Assembly VIDE pumps the binary over to a special ram disk folder on the VecFever and the VecFever detects this and loads the binary into ROM space ready for execution. This is a real help with development, it removes the other routes which involve burning roms or copying roms to sd cards.

This will help with my iteration times and allow me to basically live test on the Vectrex and see real results without worrying about emulation differences.

Thanks to Thomas and Malban my development just got that little bit more productive.


Stunt Man homebrew on Vectrex

Here’s the current state of play with my first development project on Vectrex. This project was started over Christmas. I have always loved the discrete logic game Stunt Cycle, ever since I played one of the home conversions on the TV game consoles.

I wanted something relatively simple as my first effort while I learn how to program the awesome Vectrex home games console.

Here’s a video of my current status running on one of my Vectrex machines.

This is very much a work in progress.

Current status of this version:

  • Buses displayed
  • Bike can accelerate
  • Lives
  • If jump successful buses increases
  • if jump fails lose life and attempt again
  • Title screen

It is written in MC6809 assembler, the little brother to the might MC68000 processor.

I will be fleshing the game out with other game modes and may sell this as a cartridge in the future, but will probably release the binary of the Stunt Cycle part of the game for the Vectrex community to play with.