What is Battle Mania 2P Co-op?

Battle Mania (also known as Trouble Shooter) is one of my favourite Mega Drive games. It's a fast-paced shoot 'em up starring Mania and Maria. The original game is strictly single-player: Maria follows Mania and shoots at the same time as Mania.

I've always thought the game would work really well as a two-player co-op experience, so I decided to try to make it happen. The idea is not just to add a second controllable player, but to evolve the gameplay itself into something more cooperative, where both characters are designed to work together and support each other, while respecting the spirit of the original game.

How it started

I'm not a programmer and had never done a ROM hack like this before. I'm using Cursor as an AI assistant to help me with the process. The workflow is fairly simple: the AI creates a notes/knowledge file, a script, and a patched ROM. I then test the ROM using tools like Exodus and EmuHawk, check the results, and explain what happened so we can continue iterating.

What started as a simple experiment quickly turned into a much bigger project: making Maria work as a real second player while keeping the original 1P game intact.

Current progress

• 1P / 2P mode selection on the title screen.
• 1P mode works exactly like the original game.
• In 2P mode, Player 1 controls Mania and Player 2 controls Maria.
• Both characters can move independently, shoot, and change their shooting direction. Mania currently uses an H-Flip when turning, but a new animation is planned.
• Mania can use bombs; Maria cannot. Her button will have a different function.
• A separate life and score HUD has been added for Maria, including new tiles, although it is not functional yet.
• Maria does not take damage or earn points yet.

What's next

• Fully functional HUD
• Maria's independent scoring
• Adapted bomb scoring
• Adapted bonus system
• High Score and extra-life system based on the combined score
• Maria's own damage system
• New turning animation for Mania

Since this video was recorded, the project has progressed quite a bit.

I've made a lot of progress since then, but I want to finish and polish a couple of things before making the next video.

I'll post a new update and video in the next few days.