Yes. I've made a dozen games using rollback and it really is magical. I built a strategy game in three weeks and didn't test it in multiplayer until the weekend of release. It Just Worked.
But it's not a total silver bullet from a UX perspective when rollbacks happen.
Showing a player dying and then come back to life and actually you're dead will absolutely happen. It's very weird if they were ragdolling.
If players don't have high inertia, like a platformer, they'll teleport around the place as you get the information that actually they aren't falling they jumped 100ms ago.
This is all fixable, but requires first class confirmation (i.e has the player you shot been dead longer than the max rollback window), and hand tuned interpolation on critical entities.
Luckily, I'm sure it's possible to add them to this engine.
I'm curious as to why a custom programming language was designed if the system uses WASM anyway - which you can make deterministic.
I wrote my system in C# and it worked great if you Followed The Rules (eg you must use immutable data structures). But WASM would have been a big step up.
Great to meet another rollback fan! It sounds like you have had a lot of experience with it. I'm sure I can add those things which you have mentioned - that's why we're in the beta testing phase to figure out things like this!
Why did I make a custom programming language? Well, making multiplayer automatic was only half of my mission when creating Easel.
It's a bit of a long story but the modding tools for my previous game were surprisingly successful. It became the first experience of any form of coding for a lot of people. The tool used JSON, which might sound primitive, but actually if you look past the JSON what it was really doing was defining a hierarchical declarative language for behaviour. There's something magic about that shape which allowed first-time coders to tinker without much help or documentation. (I have many theories as to why, one of them is that the hierarchy eliminates a lot of indirection that you might see in normal game programming, which means you can just kind of look at it and figure it out without jumping around. Everything is direct and in-place.)
The thing that irked me for years was, the limitations of that modding language limited not just what could be made, but what people could learn. I kept wondering what would happen if people were presented with a programming language in the same shape, but with unlimited power. Could it lay down a path for non-coders to follow all the way until they became expert coders, almost accidentally? Easel is my attempt to marry that magical hierarchical-declarative style with imperative programming in order to make a powerful language that still is extremely accessible.
I hope that, the accessibility and power of the programming language, combined with its ability to make multiplayer games automatically, will make it a super engaging choice for a first programming language for many people. I would love to see it used in schools to teach programming.
That makes sense to me!
Experienced developers are probably better off targeting WASM with Rust, but an easy on ramp to programming is definitely something that can justify a new language.