Programming grid games in assembly for VIC-20 (and Commodore 64).

Desert. Development guide

The goal of this guide is helping you in learning and writing games in assembly for Commodore computer family (mainly VIC-20) and, specially, grid games. A grid game is similar to a text adventure but it is much easier to program. One famous grid game was Hunt the Wumpus.

Almost everything works for a Commodore 64. You will find the changes for a C-64 at the end of this guide.

This development uses the Student Edition of Desert ( source code in Github. ). There are little changes between Student Edition and the final version. Final version introduces sound effects and change the color of the background.

If you found gaps in this guide, let me know.

There is a similar guide about Pursuing Tom Ram, a assembler text adventure for the unexpanded VIC-20.

Index

• Introduction. Main differences

• Introduction. ROM subroutines

• Storing data. Variables and page 0

• Storing data. Map of desert

• Locations. Main loop

• Locations. Reading input

• Locations. Flags

• Locations. Routing to locations

• Locations. Examples of locations

• Enemies. Enemy types

• Enemies. A problem with Flasks

• Verbs. Movement verbs

• Verbs. Answers to verbs

• Verbs. The Temple

• Superdesert & random numbers

• Miscellanea. Porting to Commodore 64

• Miscellanea. Porting to Commodore 16

Have fun.