C64-dev/skirmish-game/IMPLEMENTATION.md

Implementation Progress — Skirmish (C64)

Status: BUILDABLE MVP BASELINE

Last updated: 2026-05-28

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What Exists Now

Project structure

skirmish-game/
├── src/
│   ├── skirmish.asm       # Entry point, raster sync, shared state
│   ├── input.asm          # Keyboard + joystick polling
│   ├── game-logic.asm     # Turn flow, movement, combat, occupancy
│   ├── enemy-ai.asm       # Closest-target AI and movement
│   ├── render.asm         # Sprites, HUD, board markers
│   ├── data.asm           # Tables, text, sprite bitmaps
│   ├── skirmish.inc       # Shared constants
│   └── c64.cfg            # ld65 memory layout
├── docs/
│   ├── GDD.md
│   ├── TECHNICAL-PLAN.md
│   └── C64-CHEATSHEET.md
├── build.bat
├── run-vice.bat
├── debug-vice.bat
├── Makefile
├── README.md
└── skirmish.prg

Core gameplay implemented

• 8x8 tactical board with coordinate markers
• 3 player units and 3 enemy units
• Single-step turn flow:
  • player selects a unit
  • player moves or attacks
  • enemy team takes its turn
  • win/lose is checked
• Adjacent melee combat for both teams
• Unit HP tracking and death removal
• Greedy enemy AI using Manhattan distance
• Selected-unit highlight via sprite color
• Restart flow after win or loss

Controls implemented

• Q or joystick fire: cycle selected player unit
• W, A, S, D or joystick directions: move or attack
• E or space: end turn
• R: restart after game over

Engine and rendering implemented

• BASIC stub starts game with RUN -> SYS 2061
• Raster-driven frame sync installed through IRQ vector
• Main loop updates once per IRQ tick
• 6 hardware sprites used for units
• HUD shows current phase, turn count, selected unit, and all unit HP
• Sprite bitmaps and lookup tables are linked into C64-visible RAM
• Occupancy grid rebuilt from unit state to avoid stale collision state

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Build Verification

Confirmed

• build.bat assembles and links successfully with local ca65 and ld65
• Output artifact currently builds as skirmish.prg

Current artifact

• skirmish.prg size: 2617 bytes
• Most recent successful local build: 2026-05-28

Not yet verified

• Full gameplay smoke test inside VICE
• Sprite alignment and board readability in the live emulator
• Joystick port 2 behavior in VICE input mapping
• End-to-end win/lose flow by playtesting

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Known Gaps

High priority

1. Run the build in x64sc and verify the boot path, controls, and turn flow.
2. Confirm the raster-driven loop behaves correctly on a real VICE session.
3. Tune board readability if the current dot-grid is too sparse under sprites.

Medium priority

1. Add attack and death feedback such as flash or simple SID beeps.
2. Add a stronger title/opening screen.
3. Add a clearer wait indicator and maybe a per-unit action prompt.

Low priority

1. Add obstacles and richer pathing.
2. Add ranged attacks or special abilities.
3. Add difficulty scaling or multiple waves.

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Notes

• The previous tracker text described files that did not actually exist yet.
• The source tree and build scripts now exist and match this document.
• The PRG boot path was corrected so the BASIC stub jumps to the real contiguous load address.
• The next milestone should be emulator validation and gameplay polish, not project scaffolding.