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My latest vibe coded game experiment is a Command & Conquer style RTS (Real Time Strategy) game called Battle Drones (play it here). Unlike my previous experiments, this one is actually fun to play. I'm somewhat embarrassed to admit that I got there by telling Claude to "Make it a LOT more fun". It also supports multiplayer between nearby devices using audio to synchronize game state! Here's what I've built so far, and some of the things I learned along the way. Battle Drones How I built this v1: the initial prototype v2: full sprites v3: varied terrain v4: the fun update v5: Battle Drones goes 3D v8: Archipelago v10: Goliath, and agent battles Agent battles v11: Random Maps v12: Multiplayer via sound Some thoughts Update: Online multiplayer support Battle Drones My initial goal was to build an RTS game I could play on my phone, in the style of Command & Conquer. I have fond memories of the 1995 original (I liked Red Alert too) and wanted to recapture a little bit of the magic. After 12 major iterations (and 321 commits by coding agents, mainly Claude Code) I now have a browser-based game that works on mobile and desktop, has multiple play modes, several maps (including a random map generator) and even supports multiplayer for two devices within microphone range of each other. Here's a video demo of Battle Drones running in a desktop browser: <video src="https://static.simonwillison.net/static/2026/archipelago_720p_h264.mp4" poster="https://static.simonwillison.net/static/2026/archipelago_poster.jpg" preload="none" loop="1" controls="1" playsinline="1" muted="1" width="1280" height="706" style="display: block; width: 100%; height: auto;" > Features so far include: 9 buildings, 7 ground vehicles, 6 aerial vehicles, 3 infantry units - all 3D models, which you can browse here Fog of war Different weapons are needed to target aerial or ground vehicles Six maps, across five biomes - temperate, desert, arctic, volcanic, tropical A random map generator Skirmish mode - red vs. blue on a rotationally symmetrical map Last Stand mode - one player holds out against as many waves of enemies as possible Area effect weapons: Barrage, EMP, Drop Pod, Sky Hammer Crate drops with bonus resources In-game music that responds to events - it gets more intense as fighting breaks out Different in-game AI personalities (Balanced, Rush, Air Swarm, Boom, Skyforce, Ironclad) AI vs. AI mode, to watch those personalities play each other The Goliath - a giant stomping mech with laser eyes and arm cannons and the ability to establish a new base Mutators that add extra rules or twists A "Daily Op" challenge Ranks and achievements (Medals) Agent vs. Agent mode where two LLMs can play Battle Drones against each other A multiplayer mode based on two nearby phones communicating via audio messages, an extension of my earlier experiment with Chirp Pong How I built this Battle Drones is heavily vibe coded - I've reviewed almost none of the code, and it's built in a language (TypeScript) that I've hardly used myself. I've playtested it quite a bit though, and it's been through a large number of iterations since I started the project. Here's a rough history of the project so far, including key prompts and links to transcripts. v1: the initial prototype I started out with Claude Fable 5 back in July: We are going to build a mobile friendly RTS game - command and conquer style - called Battle Drones, in which two armies of drones (both flying and ground-based) battle for territory and resources Let's start with a MVP design, ask me some questions Here's a shared transcript. I'd given Claude Code for Web an environment variable with an OpenAI API key and told it to use the OpenAI Image Generation API for assets, which got me some basic sprites. You can try v1 here - it looked like this: It's recognizable as an RTS, has building mechanics and the ability to select and direct units, and a basic AI to play against. This first version was barely a proof of concept, and it wasn't any fun to play. Claude used the Phaser 2D game framework for these early versions. I didn't even realize this until several iterations later! v2: full sprites The second version (try v2 here) added sprites for all of the vehicles and the "AI vs. AI" mode, so I could watch the game playing without having to directly control it myself. Claude proved reasonably competent at prompting OpenAI's image models to generate sprites. You can browse the v2 sprites in the public/assets/sprites folder. v3: varied terrain It still wasn't much fun, and the graphics were boring. It was now October, and I had upgraded to Claude Opus 5.5. I told it: Massively improve this game. Make the graphics and gameplay better (keep it mobile friendly). Render new graphics using the latest OpenAI GPT image API (lookup details) with the API key in the environment variable. Add new unit types and balance the gameplay better. Also add new buildings and better, more varied terrain. This resulted in five new maps with generated background tiles in a variety of styles, visible here. Opus also regenerated the sprites, making them much more visually appealing. You can try v3 here - it looks like this: This is starting to feel like a real game! It still wasn't very fun to play though - I found myself getting bored pretty quickly. v4: the fun update So far my Battle Drones experiment was confirming my previous belief that coding agents can build a thing that looks like a game but can't actually make something that's genuinely compelling to play. I shared this theory with someone over dinner, and then thought to myself that I should give the models a proper chance to prove me wrong. I prompted Opus 5.5 on my phone: This game isn't fun enough yet. Make it a LOT more fun. This time I was running in Ultracode mode, where Claude Code (in this case Claude Code for Web) runs "dynamic workflows", described in their docs as: A dynamic workflow is a JavaScript script that orchestrates many subagents at once. This kicked off many hours of work. I started it in the evening and didn't get a playable result back until late into the next morning. But the results were spectacular. You can try v4 here - it looks like this: I had Claude write its own release notes - here are the highlights: Every skirmish and Daily Op now opens with a choice, gives the side that's losing a way back, and pulls the armies into the middle of the map. There are also two new ways to play. Openers: pick Blitz, Industry or Air Wing before the clock starts. Call-down powers: Barrage, EMP, Drop Pod and the Sky Hammer orbital strike. Objectives and salvage: Uplink relays, supply drops and wrecks worth scrap. Feel: combat juice, adaptive music, unit voices and an announcer. Command: battle alerts, game speed, saved squads and touch placement. New modes: Last Stand survival waves and an 8-mission Ops campaign. Progression: heroes, an after-action report with awards, a career, 7 mutators and a Daily Op. Fights run longer and swing more. In 1,200 AI-vs-AI test matches on Normal, games still undecided after 25 minutes fell from 14% to 0.9%. The share of wins by a side that had been 800+ scrap behind rose from 24% to 46%. Part of the reason Claude took so long was that it ran over a thousand simulated playtest sessions, and used the results to rebalance the existing units, add new ones, and introduce new features. v5: Battle Drones goes 3D After the success of Ultracode at "Make it a LOT more fun", I decided to be more ambitious: Port this game to three.js with 3D models for all of the buildings and vehicles and landscapes That was another overnight run. I woke up to this v5 version: The new 3D models were entirely constructed by Claude in TypeScript code. v6 (play v6 here) added some more visual polish. v7 (play v7) added robot infantry (troopers, rocket squads, snipers) and a "Condor" troop carrying aircraft. v8: Archipelago I was beginning to feel guilty at how little actual design input I had into the game - it really had been a case of me saying "make it more fun" and "add visual polish" for the past few releases. I'd noticed that the AI didn't use the new infantry and troop carrying aircraft from v7 very often - there wasn't a great strategic reason to use them. It would be neat if we had a new map with a new game mechanic that actively encouraged players to load up Condors with infantry robots and send them out into the map. This resulted in my longest prompt yet: Design a new map. Goal is to make different strategic incentives that encourage use of Infantry and Condors and aerial vehicles. To do this the map will have limited harvester resources but several more uplinks - but uplinks will be on islands that are inaccessible by land vehicles or infantry. These uplinks can also not be claimed using air vehicles. The ONLY way to get them is to fly infantry there in a Condor. Armies always start with a Condor and a single squad. If an army has no Condor a new one will be provided for free, flying in from the edge closest to their HQ and landing there. That free condor will come with a single free squad on board. The two HQs should be entirely separated by water, but still accessible by vehicles thanks to two bridges across the map in different places I want to encourage a battle over uplinks. The map should be the times the size of other maps - still square First research and then critique this design. Only build after we have agreed on any modifications You get to design a new biome for this The result was the tropical Archipelago map, with seven island uplinks that players can only capture by flying out infantry in a Condor. It's definitely the most fun map to play, once you've got the hang of the basic game mechanics from the simpler maps. The v9 edition made that map a little more interesting - it now looks like this: v10: Goliath, and agent battles I decided to add giant robot mechs to the game - think Jaegers from Pacific Rim, or Titans from Warhammer 40,000. Here are some of the prompts I used to brainstorm with Claude: Help me brainstorm ideas for adding giant robots to this game - think dreadnoughts or titans from W20K - how could we do this in a way that enhanced gameplay, kept things balanced, added unique twist? Don't overthink this yet Let's keep brainstorming. I like the idea that it's a mobile base - that can accept harvested scrap and can have buildings built near it (even if it later moves on) and can produce infantry units too. An interaction with condor would be neat but I don't know what that could be. Idea: as it gets damage it loses the ability to fire some weapons - by default it has eye laser (like lancers) and arm canons (like titan) and two shoulder mounted mortars, plus machine guns similar to a squad of troops Damage knocks out mortars and then laser - it always has guns. You can't build next to a building that was only put there because of the mech, you need the mech there for off-base building and only within three squares of it [...] Lets do two condors can carry the mech The end result is really cool. <video width="1644" height="1080" preload="none" loop="1" controls="1" playsinline="1" muted="1" style="display: block; width: 100%; height: auto;" poster="https://static.simonwillison.net/static/2026/goliath-poster.jpg" > Your browser does not support HTML video. Goliaths can be constructed using a Gantry - a building that can only be created after first building a Fab, Bay, Airpad, and Tech Lab. You can see the Goliath under construction, and it then walks out from the Gantry and can march around the map. Goliaths can "anchor", which digs them into the ground. In their anchored state they can act as a new HQ, constructing infantry units and additional buildings in a new area. Two Condor aircraft can hook onto a Goliath, at which point it can be flown around the map! The game now ends when you destroy the enemy's HQ building and any Goliaths they might have built. There are also a couple of mutators relating to Goliaths: Goliath Armada starts each side with four airborne Goliaths (each with a pair of Condors) and no other units. Robot Love adds a special rule: if enemy Goliaths get close to each other on the battlefield they fall in love and the game ends in a draw. (Thank Natalie for that one). Agent battles The other v10 feature is agent battles. In musing about how multiplayer could work I had an idea: what if different LLMs could fight it out in the game? Fun extra challenge: think about how we might make multiplayer available to coding agents. It would be neat if we could set up a battle between eg GPT-6 Sol and Claude Opus 5.5 where each model has access to a tool which gives them information about the game (presumably non-visual, but only the information they could see through fog of war etc) and lets them control their units etc [...] Consult ~/dev/llm/docs and include notes in that file about how LLM could be used here via a new tools plugin Opus 5.5 went to work on this, producing this AGENT-BATTLES.md proposal and then implementing and testing it. The feature also includes the ability to record and replay these battles - here's a replay of Claude Haiku 5.5 vs. GPT-6 Luna, and here's that same battle in a separate debug tool that shows the underlying prompt responses. The prompt that drives agent battles can be seen here. There are a few more replays like this linked in the README. I hope to turn this into a full league table at some point in the future. v11: Random Maps This version exists purely because I glanced at my Claude Usage page one day and saw that I'd only used 75% of my weekly allowance and it was resetting in 45 minutes. I decided to see if I could get an extra Battle Drones feature from my remaining tokens, and picked "random map" as the target: Design and implement a mechanism for generating a random map using any of the available biomes - it should be the size of the largest map and rivers and bridges and rocks and forest and scrap and crystals are all in play. Make them rotationally symmetric and use a seed to allow them to be selected or reused later. You have 45 minutes to build this! Be creative. Here's the transcript, and an image Claude generated to show me its work: v12: Multiplayer via sound I only just got this working, so I've not had much time to actively test it yet. The latest Battle Drones now supports multiplayer via two devices sat within microphone distance of each other! This feature started out as my Chirp Pong experiment from last week. I pointed Claude Code at that working proof of concept: Clone Simonw/tools from GitHub and look at recent branches for the example pong game that uses web microphone to implement multiplayer between two phones via audio signals Build a version of that for battledrones Opus built this Radio Probe tool to measure how much bandwidth we could get between two devices and, based on positive results from that, implemented a full audio modem system. I've tried it between laptops, iPhones and iPads so far and it seems to work really well! Why use sound for this? Because I love static HTML that costs nothing to run, and I don't want to spin up a server somewhere and then stay responsible for keeping it operating for as long as anyone might want to play the game. Some thoughts I know almost nothing about game development. This makes it a great opportunity to try out coding agents in a field where my existing software engineering experience has less impact on the results. Games are also super low stakes. The worst that can happen is one of my silly game experiments suffers a bug. This morning (via Hacker News) I found Steam Fans Are Begging for a No-AI Filter as Steam Next Fest Is Filled With Slop. I wouldn't personally dream of submitting Battle Drones to an event like this - it's still way too low effort to warrant consideration as a legitimate indie gaming project. ... but I can now see a path to vibe coded games like this being taken seriously. Battle Drones is fun, it looks good, it has innovative features (the multiplayer-over-audio thing is a first for an RTS as far as I can tell). I'd love to see what someone with better taste than me and a driving passion to produce something truly exceptional could build! A few other observations from this project: Static HTML and JavaScript is a fantastic medium for games development. WebGL works great, and Three.js (and Phaser before it) are excellent platforms to build on that the current models know inside out. This also lets them run as Progressive Web Apps - I didn't ask for it, but Battle Drones works offline. I was able to play it on a plane despite never having directly installed it - my phone had it cached. Giving Claude an OpenAI API key and telling it to generate images using OpenAI's models works really well. It can view the images it has generated and iterate on the prompts. Opus 5.5 is spectacular at 3D modeling using Three.js (and Blender, and no doubt other 3D applications as well). The same is true of GPT-6 Astra. They are absolutely capable of building models for 3D game projects. For features like replay and multiplayer it's useful to have a deterministic simulation engine. At one point Claude had to replace calls to Math.sin() and Math.cos() and friends with custom versions because different browsers (Chrome vs. Safari, for example) returned very slightly different numbers, desynchronizing the replay. Opus 5.5 can write music! There are no audio files in this project - the soundtrack is entirely generated through code, varies across different maps, and even gets more intense as the battle heats up. See Scrimshaw Jukebox for a previous experiment with Claude for music composition. I still can't get over how well the prompt "Make it a LOT more fun" worked. Tools are effectively free. I prompted up the Radio Probe, the Model browser, the Agent vs. Agent debug tool, and Claude Code built a bunch of tools for itself that I haven't even explored myself. Audio-based multiplayer between static HTML games works! I hope to see a whole lot more games use this same pattern - in digging around today I've not found much prior art beyond Siner by Alon Horesh and ggwave by Georgi Gerganov (also of llama.cpp fame). Claude Code "Ultracode" burns tokens like there's no tomorrow, but it can also solve complex problems (like adding audio-based multiplayer) from a single prompt. I'm still not quite over the guilt of building software in this way. I don't feel like I've earned the right to create something this good, in a field in which I have so little prior experience! At this point I've shown it to enough people in private that it felt wrong not to publish it for everyone else to see and learn from. Update: Online multiplayer support Earlier in this article I said: Games are also super low stakes. The worst that can happen is one of my silly game experiments suffers a bug. Then I tried playing the multiplayer version with Natalie... and the high pitched modem sounds gave her a nasty headache! That's a pretty bad bug. I added a warning and was then inspired to build proper network multiplayer. I tried getting WebRTC to work but couldn't get a connection going between two of my own devices even on my own WiFi network, so I had Claude build a simple, stateless WebSockets relay server instead: If I wanted to support multiplayer between two devices at a very low cost without storing any state on the server could I do that with a tiny asyncio web server running on the cheapest Fly instance? Build the server and the fly.toml for deploying it, use Fly application name battledrones-relay - put that in a folder in the repo, include deploy instructions in the README in that folder Here's the resulting server. Since this scales to zero and runs on a single Fly.io shared-cpu-1x instance it should cost me no more than $2.19/month - and that's if it stays hot and serving connections the whole time. Battle Drones now supports online multiplayer. Click "Duel a friend online", then either share the resulting room URL via your messaging app of choice or have them snap a picture of the displayed QR Code. I also added a feature where you can copy JSON of the match once it has ended and then feed that into the replay feature to rewatch your game. I didn't expect to introduce online multiplayer this soon, but the headache bug felt like it warranted an urgent alternative. Tags: game-design, projects, ai, generative-ai, llms, claude, vibe-coding, coding-agents, claude-code