Flicky (Genesis) Disassembly

Disassembly of Flicky for Sega Genesis/Mega Drive. The source assembles with the AS Macro Assembler to produce a byte-accurate ROM.

This project is based on approaches from alien_soldier_src.

AS Assembler: http://john.ccac.rwth-aachen.de:8000/as/index.html

Quick Start

git clone <repo>
cd flicky_src

# Place original ROM in project root:
#   Flicky (UE) [!].bin

make init           # Extract data, build ROM, create reference
make compare        # Verify build matches reference

Project Structure

flicky_src/
├── bin/                    # Assembler tools
│   ├── asw.exe             # AS Macro Assembler 1.42 Beta
│   ├── p2bin.exe           # Object to binary converter
│   └── *.msg               # Assembler message catalogs
├── data/                   # Binary data segments (generated by make init)
│   ├── artnem/             # Nemesis-compressed graphics
│   ├── arteni/             # Enigma-compressed tilemaps
│   ├── artunc/             # Uncompressed graphics
│   ├── sound/              # Sound data (Z80, DAC samples)
│   ├── other/              # Other binary data
│   └── data_addrs.txt      # Addresses for ROM extraction
├── tools/                  # Compression/decompression tools
│   ├── nemesis_dec.c/py    # Nemesis decompressor (C and Python)
│   ├── enigma_dec.c/py     # Enigma decompressor (C and Python)
│   └── Makefile            # Build C tools
├── scripts/                # Python build and analysis tools
├── src/                    # Include files
│   ├── macros.inc          # Assembler macros
│   ├── ports.inc           # Hardware I/O port definitions
│   ├── equals.inc          # Constants and equates
│   └── ram_addrs.inc       # RAM address definitions
├── workflow/               # Documentation workflow state
├── flicky.s                # Main disassembled source (~10k lines)
└── Makefile                # Build system

Make Targets

Basic Commands

make init           # Initialize project (requires original ROM)
make build          # Assemble source → fbuilt.bin
make compare        # Compare built ROM with reference
make split          # Re-extract binary data from original ROM
make tools          # Build C decompressor tools
make unpack-data    # Decompress Nemesis/Enigma data
make clean          # Remove all build artifacts
make help           # Show all available targets

Analysis Workflow

Automated procedure analysis using emulator screenshots:

make reference MOVIE=longplay   # Generate reference screenshots
make find-unanalyzed            # Find procedures needing analysis
make analyze MOVIE=longplay     # Run automated analysis
make report MOVIE=longplay      # Generate analysis report

Documentation Workflow

Semi-automated procedure naming with Claude AI:

make set-movie MOVIE=longplay   # Set movie type for session
make prepare-batch COUNT=40     # Prepare batch of procedures
# → Claude reads workflow/batch_procedures.txt
# → Claude creates workflow/rename_batch.csv
make rename                     # Apply renames to source
make build && make compare      # Verify ROM unchanged

Utility Commands

make show-movie     # Display current movie setting
make stop           # Kill running Gens emulator instances
make build-gens     # Build modified Gens emulator (VS2022)

Scripts

Script	Purpose
analyze_procedures.py	Automated procedure analysis with emulator
build_rom.py	Orchestrates ROM assembly (AS → p2bin)
clean_project.py	Cross-platform cleanup of build artifacts
compare_roms.py	Binary comparison of built vs reference ROM
extract_data_addrs.py	Extracts data addresses from source file
find_unnamed_procedures.py	Lists procedures still named sub_*, loc_*
generate_analysis_report.py	Generates report from analysis data
init_project.py	Full project initialization (split → build → reference)
prepare_batch.py	Prepares batch of procedures for documentation
rename_procedures.py	Applies rename CSV to source file
split_data_from_rom.py	Extracts binary data segments from ROM
unpack_data.py	Decompresses Nemesis/Enigma data files

How to Build

Prerequisites

• Python 3.x
• Make (Git Bash / WSL on Windows)
• AS Macro Assembler (included in bin/)
• Original ROM: Flicky (UE) [!].bin

First Time Setup

# 1. Place original ROM in project root
#    Flicky (UE) [!].bin

# 2. Initialize project
make init

This will:

1. Extract binary data from ROM → data/*.bin
2. Build ROM from source → fbuilt.bin
3. Create reference ROM → flicky.bin

Regular Development

make build      # Rebuild ROM
make compare    # Verify matches reference

Game Information

Title	FLICKY
Platform	Sega Mega Drive / Genesis
Release	February 1991
Product Code	GM 00001022-00
ROM Size	128 KB
Regions	Japan, USA, Europe (JUE)

Known Issues

Pointer Hardcoding at $10000

When adding padding before Sys_GameEntryPoint (address $10000), the game freezes in certain places. This is caused by hardcoded pointer offsets in data/data_z80_part2.bin that don't get recalculated when the ROM layout shifts.

The code in Sound_LoadZ80Table uses suba.l #Sys_GameEntryPoint,a0 to convert offsets, but the offsets stored in the binary data file remain unchanged.

Workaround: Keep Sys_GameEntryPoint at exactly $10000.

Credits

• Based on approaches from alien_soldier_src
• AS Macro Assembler by Alfred Arnold
• Original game by Sega (1984/1991)

License

This is a work of reverse engineering for educational and preservation purposes. The original game is copyright Sega.