Game Template

Introduction

This is a template project for creating games to run on the following neo-retro platforms:

• Agon Light 2
• Aquarius+
• Commander X16
• ZX Spectrum Next

See peteshobby.com for more detailed information.

Building the template

Each platform has its own make file. If you are using Visual Studio Code the project includes build task definitions so you can just press Ctrl-Shift-B and select the target you want to run.

SDKs

The template expects the following SDKs to be installed:

Platform	SDK
Agon Light	AgDev
Aquarius+	Aquarius+ SDK
Commander X16	cc65
ZX Spectrun Next	z88dk

Basic Game Structure

graph TD;
    A(Initialization)-->B[Splash Screen];
    B-->C[Attract Screen];
    C-->D[Game Loop];
    D-->C;

Loading

Initialization

Each system is initialize to run as fast as possible and to provide roughly similar capabilities.

The project declares one initialization function and each platform defines its own version of that function. The initalization functions call several sub-functions than initialize different components.

One of the reasons it is arranged this way is to make it easier to move those sub-functions to banked memory to leave space for the main game code.

Sprites and Tiles

Both sprite and tile graphic data are defined in the same array and copied to the appropriate places in memory on initialization.

Text overlay

The template uses a text overlay for showing the score and other information.

The Agon Light does not currently have the capability to provide a real text overlay. However the tilemap can be configured to only cover the top 200 lines of a 240 line screen.

Even with this games will run noticably slower on the Agon compared to the other systems. Also because it is not a real overlay sprites will always appear above it. The template hides this by limiting the area of the screen the sprites appear in.

All the other systems have a real text overlay capability.

Splash Screen

The splash screen is shown once immediately after the game loads.

Its purpose is to display copyright and contact information and as a place to troubleshoot any initialization issues.

Attract Screen

The attract screen is shown after the splash screen and in between games. It shows the instructions for playing the game and waits for the player to start the game.

The Game Loop

The game loop:

• Moves the tilemap
• Updates the sprites
• Updates the text overlay

Configured Capabilities

Agon Light

• 320 x 200 screen resolution
• 64 color palette
• 64x32 tilemap 8x8 tiles
• 256 sprites
• 20Mhz ez80 CPU
• 24 bit address bus
• Available memory:
  • 512K without banking

Aquarius+

• 320 x 200 screen resolution
• 4 x 16 color palettes
• 64x32 tilemap 8x8 tiles
• 64 sprites
• 7.16Mhz Z80 CPU
• 16 bit address bus
• Available memory:
  • ~50K without banking
  • 512K with banking

Commander X16

• 320 x 240 screen resolution
• 256 color palette
• 64x64 tilemap 16x16 tiles
• 128 sprites
• 8Mhz 65C02S CPU
• 16 bit address bus; available memory:
  • ~38K without banking
  • 512K with banking

ZX Spectrum Next

• 320 x 256 screen resolution
• 6 x 256 color palettes
• 40x32 tilemap 8x8 tiles
• 128 sprites
• 28Mhz Z80N CPU
• 16 bit address bus; available memory:
  • ~32K without banking
  • 768K with banking