--- title: "Grapplenauts: Multiplayer Brawler + Creator Interview" subtitle: "How one dev built a real-time zero-gravity arena brawler with Phaser, Colyseus & TypeScript" date: 2026-03-13T17:00:00.000Z category: game url: https://phaser.io/news/2026/03/grapplenauts-phaser-multiplayer-browser-game site: Phaser - https://phaser.io copyright: © 2026 Phaser Studio Inc. All rights reserved. --- # Grapplenauts: Multiplayer Brawler + Creator Interview *How one dev built a real-time zero-gravity arena brawler with Phaser, Colyseus & TypeScript* ***Grapplenauts*** is a zero-gravity arena brawler built with **Phaser** and **Colyseus**, where players move around with a grappling hook, collect coins, and buy upgrades to become the most powerful player in the lobby. Created by [Conner Lane (@seltzerfish)](https://seltzerfish.com/), with art by [Nate Sandhart (@unlevelednate)](https://www.tiktok.com/@unlevelednate), the game was built as a challenge to ship a production-ready multiplayer browser game from scratch. ## A Multiplayer Browser Game Built on Phaser and Colyseus ***Grapplenauts*** is an io-style brawler featuring real-time online multiplayer, physics-based movement, and a dynamic upgrade system. Players collect coins to purchase upgrades from vendors scattered around the map, covering grapple mechanics, shields, and jetpacks. The map is filled with hazards like throwable bombs, pinball bumpers, and an eldritch horror that occasionally spawns to eat players. The game was built during Conner's time at the **Recurse Center**, a programming retreat, as a deliberate push to expand his technical skills into real-time multiplayer. ![](grapplenauts-1.png) ## Why Phaser and Colyseus The combination of **Phaser** and **Colyseus** works particularly well for browser games for one key reason: both are pure JavaScript. Game logic that needs to run on both the client and the server can be written once in **TypeScript** and executed identically in both environments, making the system more stable and easier to debug. **Phaser** handles rendering and visual effects smoothly, while **Colyseus** manages WebSocket connections on the server side. Conner runs the server on the **Bun** runtime rather than Node, which he notes helps significantly with performance. ## Grappling Hook Physics The grappling hook was a natural starting point for Conner, who has long favored it as a game mechanic. Rather than linear constant movement, the hook creates locomotion through a dynamic pulling force, offering what he describes as simple to grasp but with a lot of emergent complexity. Under the hood, the grapples use a spring calculation to determine the pulling force, with the feel tuned primarily through the spring's stiffness constant. ## Creator Interview **Q: How would you describe *Grapplenauts* and its core mechanics?** A: The elevator pitch: ***Grapplenauts*** is a zero-gravity arena brawler where you move around with a grappling hook, and collect coins & powerups to become the most powerful player in the lobby! More specifically, collecting coins allows you to purchase upgrades from various vendors on the map. There are vendors for grapple upgrades, shield upgrades, and jetpack upgrades. Every upgrade you get makes you more powerful and puts you higher on the leaderboard, but they get more expensive. There are also a bunch of hazards and events around the map, like bombs that you can grab and throw, pinball bumpers that you can bounce off of, and an eldritch horror that occasionally spawns to eat players. **Q: What inspired you to create *Grapplenauts*?** A: I've made a lot of small games as a solo dev, but not many featuring online multiplayer. I wanted to expand my technical ability, so last year (2025) while attending a programming retreat called the **Recurse Center**, I challenged myself to make a production-ready multiplayer browser game. That game became ***Grapplenauts*** 🙂 **Q: How did you come up with the grappling hook as the core mechanic, and how hard was it to get it feeling right?** A: Grappling hooks have always been a favorite mechanic of mine, so it felt like a very natural starting point for me. I love the feeling of locomotion via a dynamic pulling force, rather than just linear constant movement. It's one of those things that's simple to grasp, yet has a lot of "emergent complexity", so there's a lot of finesse and skill expression to be had when playing with it. Under the hood, the grapples use a spring calculation to determine the pulling force, so getting the feeling right was mainly a matter of tuning the spring's "stiffness" constant. **Q: Why did you choose Phaser and Colyseus? How has that combination held up for a real-time multiplayer physics game?** A: For a browser game, **Phaser** and **Colyseus** work super well together for one big reason: they're both pure JavaScript. There's a lot of game logic that runs on both the user's browser and the game's server; being able to just write that code once (in **TypeScript**) and have it run exactly the same in both locations makes the whole system much more stable and easier to debug. Performance-wise, **Phaser** is buttery smooth with the rendering and visual effects, and **Colyseus** does a great job handling websocket connections on the server. It's worth noting that I'm running the server with the **Bun** runtime rather than Node, which helps a lot with performance. **Q: What has been the biggest challenge so far** A: With multiplayer games, there are a lot of hurdles that arise around how state is represented and communicated. Chiefly, it's hard to keep players in sync with each other smoothly. Every player in a lobby is running their own simulation of the game, and small variations in physics input can cause drastically different outcomes. That's why for a game like this, you need an "authoritative server", which keeps the True State™️ of the game world, and clients (player devices) must "reconcile" their state with the server state. In other words, when the data about the game coming in from the server looks different than what is represented locally, the client must alter its own state to match the incoming server state. But it can't do that too abruptly, or else it looks glitchy and choppy. So there's some smoothing that has to happen with the reconciliation process. On top of that, this whole system is complicated by the fact that it takes time (usually 50-200ms) for data to travel back and forth from client to server, so the game state has already changed by the time the server's response arrives. The TLDR here is that networking is hard. **Q: Which part of the game are you most proud of?** A: From an engineering perspective, there's a fun trick I did with level generation: when a client joins a lobby, the server must communicate information about the lobby so that the client can build the lobby locally. But instead of sending size and position data about the hundreds of randomly generated terrain bodies in the map, the server simply sends the random seed (a single string of characters) it used to generate the lobby, and the client uses its own shared code to "randomly" generate the exact same map. This is only possible due to the fact that the client and server are both written in JavaScript. From a gameplay perspective, I love that all the audio effects in the game have a slight doppler effect. Sometimes those silly unnecessary features are what give the most personality. **Q: Where is Grapplenauts right now in its development, and what's coming next?** A: The UI and menus could use some love, but the gameplay in ***Grapplenauts*** is mostly feature complete. As for what's next, I'd really like to get it hosted on a platform like **Poki** or **CrazyGames** sometime soon so that it can reach a wider audience. I don't have any major updates planned right now, but that could definitely change if it gets popular on one of those platforms 🙂 **Q: What advice would you give to someone wanting to build a multiplayer browser game from scratch?** A: I would stress the importance of figuring out exactly what the mechanics are going to be before you start writing any networking code. Iterating on features and gameplay is hard in a single player game, but it's 10x harder and more costly once there's a server involved. With ***Grapplenauts***, I made the mistake of not knowing exactly what the core gameplay loop was going to look like when I started, and I spent a ridiculous amount of time implementing experimental features, interactions, and entities... most of which ended up being scrapped. I could have saved myself a ton of time by figuring out my mechanics in a local environment (no networking involved), and THEN made it multiplayer. ----- ***Grapplenauts*** is open to play in your browser. 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