Online multiplayer party game called Ignited

[MariusLab]

So about 1 year ago I started working on this online multiplayer party game using Jolt physics to drive pretty much all gameplay https://store.steampowered.com/app/4311700/Ignited/

The game is built using Unreal 5. The characters in the game are fully simulated physics objects. They carry hammers that you control using your mouse. By swinging the hammer you get to move your character around, there is no other way to move. Kind of like the infamous game "Getting Over It" by Bennett Foddy. But on top of that you are also fighting the other player for objectives or just in a classic deathmatch.

The more interesting part is that online multiplayer works by exchanging player inputs ONLY. Game state is never exchanged between clients. That is achieved by ensuring the game is fully deterministic and produces the same exact output on multiple machines given the same set of inputs.

The game is also 2D. It really put Jolt to the test on that front and on determinism. I can say that in both of those fronts it has never failed me. I've fixed hundreds of bugs and in every single case it was my own code that was at fault.

So if anyone is thinking of using Jolt for a deterministic online multiplayer game - it's absolutely solid for that. Once you understand how it all works and you have your own games framework working with rollbacks, it is a joy to add new features to multiplayer. Normally you'd have to think about replication and client side prediction with every little new thing you want to add to your game. But when you're only exchanging inputs over the wire you're really adding features like you would to a single player game. At least to a certain extent.

Having said that, setting it all up and fixing all the bugs was a huge technical challenge. I was about 8-9 months into development when I finally caught the last few nasty bugs and online multiplayer started working in a stable manner. So it's a huge upfront technical cost.

The game was meant to be a commercial release and I was planning to share it here once it was out, however I'm not sure about its future anymore. I ran into some serious issues during playtesting. Nothing to do with Jolt or online play. The issue is most players find the controls unintuitive and way too difficult. I improved them a lot based on feedback, but it's just not enough and I've lost faith. New players just bounce off the game as soon as they try to move. Feel free to request a playtest on Steam if you want to give the game a shot yourself. It should grant access instantly.

I want to thank jrouwe for making this amazing library and giving it to us for free. It is an amazing piece of engineering. I've had to go through a lot of the source code to solve issues and the code is super clean and readable. Thank you!

[jrouwe]

Thanks for the kind words! It does look like a fun game. Can I have a code?

[MariusLab]

The code is on a privately hosted Perforce repo. But when the master asks, you must provide. I put it on github for anyone curious https://github.com/MariusLab/Ignited.

I'll be honest about the quality of the codebase, I was a solodev on this project and my priority definitely wasn't to keep things clean or well documented. It's a bit of a mess. But if you need inspiration for determinism or working with Jolt in Unreal - it might help.

For anyone curious:

Main game loop starts here GameLoopSubsystem::Tick(float DeltaTime).

I recommend reading SpawnerSubsystem.cpp for a lot of BIG and useful comments I left for common rollback pitfalls when spawning and rolling back Jolt bodies.

JoltSubsystem.cpp is another interesting one. Mostly a wrapper around Jolt, so we're not using it directly and can add any additional logic needed.

GameStateManager.cpp - saves/loads game state for rollbacks.

[jrouwe]

The code is on a privately hosted Perforce repo. But when the master asks, you must provide. I put it on github for anyone curious https://github.com/MariusLab/Ignited.

Oh sorry, I did not ask for 'the code' but for a 'Steam code'.

[MariusLab]

Ahh, I misunderstood that. But it's good, maybe it can help someone else out who sets out to build something similar.

A steam code isn't required at the moment. If you just go to the Steam page and press "request playtest access" it should grant it immediately.

[jrouwe]

I can't make it past this level:

Jumping on top of those floating platforms is too hard for me (my brain short circuits trying to move the mouse in circles). I would suggest that you can propel yourself yourself in the direction opposite of the hammer by pressing (holding for more power?) the mouse button. Or maybe pressing the left/right button should automatically spin the hammer counter clockwise/clockwise so that you don't need insane 'move mouse in circles' skills. You could probably even keep the current controls alongside this so that people who are able to master the controls have more fine grained control over the character.

I can see that you put a lot of effort in this, I would say it should be possible to tweak the controls to make it fun.

[MariusLab]

Really appreciate you giving it a shot! You're not the first to run into this problem. The thing is that you CAN propel yourself in the direction opposite of the hammer. You don't need to do circles. Circles is just one way to move forward. You can move the hammer below the character slowly, and the character starts to rise up. If you do it quick enough, the character will "jump".

I suspect the issue why people don't discover this automatically is due to mouse sensitivity. It's most likely either way too high or way too low for the movement to work correctly for you. I don't know if I could automatically tune the sensitivity for optimal gameplay. Cause the player himself doesn't know yet what "optimal gameplay" looks like.

[jrouwe]

The thing is that you CAN propel yourself in the direction opposite of the hammer.

I did discover this, but I couldn't jump high enough using this technique / and I had problems aiming my jumps.