9 ms·
Technical Breakdown of a new NES game written in Lisp
- j_m_b 7y agoOne of the advantages of lisp is REPL-driven development. I imagine you can't just edit a fn, eval it and then see the changes immediately. What is the workflow like when creating a NES game using co2?
- bitwize 7y agoI dunno about Co2, but the last time I heard about a project like this -- Naughty Dog's GOAL -- they absolutely could compile GOAL on the fly on the development PC and send it immediately to run on the PS2 dev kit inside an already running game. REPL-driven development directly on a game console. It was awesome.
- jasperpilgrim 7y agoThis is impressive. I appreciate you documenting the development of it and giving an overview of what's going on inside. I wish there were more blog posts like this. Have you reached out to the Racket community about the game and co2? Also, would you say this Lisp is geared more toward people who already know 6502 assembly, and not toward people who just want to write a NES game in a Lisp?
- djmips 7y agoWith only looking through the article and being a 6502/NES programmer myself, you can't escape having to know 6502 and the NES hardware to write a NES game. This Lisp is cool and it will certainly smooth the process and is a good fit for an Adventure game and other parts of NES game development where you aren't counting cycles (like UI).
- jasperpilgrim 7y agoGood to know. Assuming it's true that 6502 asm is not too difficult to learn, co2 looks like it would be fun to work with on a simple game. Really neat project.
- djmips 7y ago6502 is easy to learn. Have some fun here https://skilldrick.github.io/easy6502/ https://skilldrick.github.io/easy6502/ For me the challenge with the NES itself was getting a good tutorial and then with making a game, getting your art from your mind into the tiles and sprites and in your project. Your art 'pipeline'. Once that's established it becomes easier.
- ninkendo 7y agoI know it's off-topic but I appreciate so much when somebody hosts their own blog rather than using Medium or some nag-ware hosting service. I didn't get any pop-up "pardon[ing] the interruption" or asking me to join a mailing list, or anything! To think this used to be the normal way of doing things on the web.
- deleted 7y ago[deleted]
- scrollaway 7y agoThe other side of that coin is that on mobile the article is painful to read and the layout is horrible. For what it's worth I hate medium as well. But I would recommend ghost.org if you want to go with self hosting.
- savolai 7y agoAlso choosing a good wordpress theme helps a lot. :)
- ihuman 7y agoThe post is using [0] this theme, which hasn't been updated in over 6 years. [0] https://wordpress.org/themes/duster/ https://wordpress.org/themes/duster/
- shantly 7y ago> The other side of that coin is that on mobile the article is painful to read and the layout is horrible. Looks reader-mode-compatible in Safari, which solves the problem for any site that's mostly content.
- ngcc_hk 7y agoSeems ok reading in my mobile safari, not even using reader mode.
- 7y ago
- nudpiedo 7y agoThis is a complete and absolute hack and I love it. When reading the README file of their github it is possible to see how "impure" pragmatic decisions were made like for loops and not supporting proper recursion. I wish there would be more projects like this one porting lisp runtimes to more and more hardware. In the other hand the racket lisp behind the scenes _generates_ the assembly code based on some of the scheme primitives rather than porting its whole Racket runtime there, which in spite of not being the same as running a lisp in the NES hardware is still impressive.
- TurboHaskal 7y agoMost Lispers and some Schemers are quite pragmatic in that regard. With the former favouring OOP and looping over recursion and the latter using imperative code when it matters. With developer mindshare flocking to the Haskell view of FP, for the Lisp family, only the Clojure users seem to still hold purity in high regard.
- agentultra 7y agoPurity isn't in contrast with pragmatism; what Haskellers refer to as purity is referential transparency. You can still do this kind of work in Haskell as well. It is a great imperative language. Though as someone who has written assembler compilers in Common Lisp... it's felt relatively easy to do in CL. I've only heard people talk about writing control software for drones from Haskell. I have no idea how one would do that in practice though.
- kryptiskt 7y agoHere is a blog about assembling 6502 code in Haskell: http://www.wall.org/~lewis/2013/10/15/asm-monad.html http://www.wall.org/~lewis/2013/10/15/asm-monad.html
- ska 7y agoWith the former favouring OOP and looping over recursion Not my experience at all, fwiw.
- CoolGuySteve 7y agoI’d like to hear more about the compiled stack. In extremely latency sensitive applications, the mix of stack and instruction cacheline faults can cause significant overhead.
- zozbot234 7y agoNo cache lines on a 6502, though!
- CoolGuySteve 7y agoI'm talking about modern architectures
- aidenn0 7y agoI've only heard this term used with PIC development tools. It makes all local variables have a fixed place in RAM. This obviously removes support for recursion. A naive implementation would cause this to explode memory usage. However, you can analyze your entire program and any variables (including across function boundaries) that are never live at the same time are now allowed to share storage. Now you never push or pop variables to your stack, and your dynamic stack size is only the maximum call depth (no frame pointer needed because you don't have any on-stack variables, so you only save the return pointer to the stack).
- reikonomusha 7y agoThis was an incredibly enjoyable read. A lesson to take away is that many of the ideas of Lisp can be taken advantage of without reeling in the entirety of an existing stack. Writing a Lisp parser is easy. Walking Lisp code is easy. Serializing Lisp code is easy. Adding a new primitive is easy. Adding very basic syntax transforming macros is easy. All of these are virtually trivial if your host language is a Lisp, as was the case with Co2. What they didn’t do is what many people might think are table stakes with Lisp: writing a garbage collector, writing a runtime, supporting lambdas, and so on. Those are unreasonable asks for 2K RAM on a 6502. I wouldn’t say they wrote a bonafide Lisp, but they made use of many ideas of Lisp successfully to write a game that is very surprisingly readable while not being too abstract over assembly. Since Lisp began in the 1950s, it has always needed to stay tied to the low level. Even today, with SBCL or CCL, you can write your own assembly code. One relevant thing to the article is Baker’s COMFY 6502 language for writing assembly code [0]. A few implementations can be found on GitHub. [0] http://home.pipeline.com/~hbaker1/sigplannotices/sigcol04.pdf http://home.pipeline.com/~hbaker1/sigplannotices/sigcol04.pd...
- zozbot234 7y agoIf you aren't going to have a GC, "rich" runtime or lambda support, what does LISP really bring you over FORTH? And implementations of the latter on 6502 have been commonplace since the 1980s...
- djmips 7y agoHard reasons. Forth implementations on the 6502 uses a stack and require more RAM than Co2 which uses a compiled stack. I feel like Co2 would compile to faster code but of course I haven't benchmarked this. The reason I feel this is so is that I way I understand compiled forth is that the 'words' are still threaded so you don't escape the interpreter overhead. Soft reasons. Co2 takes away the chore of parsing, in Forth you are the parser. It's simpler but more error prone and harder to read (subjectively). Forth is postfix notation which for a lot of people is challenging.
- asguy 7y ago
- drcode 7y agoI'm struggling with the same problem: I'm a Lisp programmer who's writing a commercial game, in my case a Unity engine game, which requires C#. I've opted for a less elegant, but technically simple strategy: I'm writing all the build tools/content tools in Clojurescript, and then writing only the core game engine in raw C#. Next, I'm using http://bridge.net http://bridge.net to cross-compile the game engine into javascript, which I can then link to from clojurescript so that all unit tests and 90% of all QA testing can be done via clojurescript tooling, without any C# in sight. This allows me to deploy a commercial game in "native" C# without any performance penalty, but with as few lines of C# as humanly possible.
- mikepurvis 7y agoThis seems really complicated, relative to using the Clojure CLR port. Is it just not mature enough, or were there other advantages to going via JS?
- drcode 7y agoUsing Clojure CLR would make the build process simple, at the cost of some complexity and likely a performance penalty in the deployed application. On the other hand, my strategy makes the final deployed application dead simple and fast, but leads to a build process that's complex and messy. It seems objectively true that the latter approach is going to be less risky, because if the final deployed game doesn't work well, the whole project is f###ed. The only way to mitigate this risk and still stay with 100% Lisp is to create your own Lisp compiler, which is exactly what OP did... but that way lies insanity :)
- outworlder 7y agoThat sounds like a great approach. I often wondered how to get Scheme code running in Unity. Can you fire up a REPL while the game is running? That would be huge. Many years ago I experimented with the idea of creating games for iOS in Chicken Scheme. Because I'm exceedingly lazy and did not want to bother with cross-compilation – unless it became a serious project – I just told Chicken's compiler to stop at the C code generation step. The Makefile would then copy the generated (and quite unreadable) C code to the XCode project, and then compile the whole thing together with any Objective-C code I had. With very little setup code, you could embed arbitrarily large Chicken programs. And given Chicken's excellent C interop, the Objective-C code could easily call Scheme functions (the reverse is not as trivial, so I just wrote wrappers for the handful of Objective-C functions I needed – which weren't many in a game). The only piece missing at the time was that Chicken did not have OpenGL-ES bindings. I solved that by copying code from Gambit Scheme, and using a couple of very trivial macros to make it compatible. That worked beautifully. I could even start a remote REPL and instantly change running code over the network, no matter if it was running in a real device or the simulator. And I mean instantly: the next rendered frame would already have the changes. Then I hit my roadblock: I had successfully solved the technical problem, so I lost interest in pursuing the game, which was ostensibly the reason why I had embarked on this detour to begin with. Oh well.
- seisvelas 7y agoThey made their language using Racket! Great to see Racket style Language Oriented Programming being used for something so cool
- ngcc_hk 7y agoVery impressive and readable. Congratulations!!!
- gautamcgoel 7y agoReally cool article. I appreciated the "engineering on the battlefield" vibe. I'm curious why they first went with Lisp.
- emptybits 7y agoI loved Lisp upon my first exposure in the late 80s in university. Then I "had" to professionally abandon Lisp leanings because I entered the game industry which required, at the time, a commitment to 8-bit assembly code. No problem. Lisp remained a hobby. Fast forward! Unexpected intersect! I love this so much and thank you for the great writeup! There's a podcast for present day NES developers called The Assembly Line.[1] I'm sure they'd enjoy this story and talking to you. [1] https://soundcloud.com/nesassemblyline https://soundcloud.com/nesassemblyline
- anon9001 7y agoIf you like this, you should also check out the work around Retro City Rampage. RCR is a GTA1 clone for multiple platforms from a few years back, but the developer also made a real NES ROM of it. Here's a great talk about that process: https://www.youtube.com/watch?v=Hvx4xXhZMrU https://www.youtube.com/watch?v=Hvx4xXhZMrU (I'm not related to the project, but it's one of the few games I've 100% completed because it was just so good)
- soulofmischief 7y agoCool! Thanks for sharing! Just picked up the game, it looks awesome.
- fouc 7y agoLooking at the code examples of the entity system in this article made me wonder what it'd be like to code a MUD in this language or in lisp generally. Does anyone know if there are any MUDs out there coded in lisp? I didn't find any good results in google aside from the MPI lisp-like language built on top of FurryMUCK.
- 320x200 7y agoA bit tangential, in relation to MUD-like games and Lisp. The original author of co2 (that is to say before it was developed further by OP), has worked on a multi-user interactive fiction with some of the other persons who worked on this NES game. For that he used mzscheme to run a server side virtual world of bots/NPC interacting with the players via a browser/javascript client. You can find some information there: https://archive.bleu255.com/nakedonpluto/about/ https://archive.bleu255.com/nakedonpluto/about/ https://gitorious.org/naked-on-pluto/game-server https://gitorious.org/naked-on-pluto/game-server (cert expired) https://gitorious.org/naked-on-pluto/game-client https://gitorious.org/naked-on-pluto/game-client (cert expired)
- edmoffo 7y agoLisp is and was the best programming language. I moved to Java many years ago and still regret :)