Each map block was 2x2 cells, and each cell, 8x8 pixels. Made rendering background cells and fog-of-war overlays very straightforward assembly language.
All of Warcraft/etc. had only a few thousand lines of assembly language to render maps/sprites/fonts/fog-of-war into the offscreen buffer, and to blit from the offscreen buffer to the screen.
The rest of the code didn't need to be in assembly, which is too time-consuming to write for code where the performance doesn't matter. Everything else was written in portable assembler, by which I mean C.
Edit:
By way of comparison, Blackthorne for Super Nintendo was all 85816 assembly. The Genesis version (Motorola 68000) and DOS version (Intel 80386) were manually transcribed into their respective assembly languages.
The PC version of Blackthorne also had a lot of custom assembler macros to generate 100K of rendering code to do pixel-scrollable chunky-planar VGA mode X (written by Bryan Waters - https://www.mobygames.com/person/5641/bryan-waters/).
At Blizzard we learned from working on those console app ports that writing assembly code takes too much programmer time.
Edit 2:
I recall that Comanche: Maximum Overkill (1992, a voxel-based helicopter simulator) was written in all assembly in DOS real mode. A huge technical feat, but so much work to port to protected mode that I think they switched to polygon-rendering for later versions.
EA a while back released the source code to (most) of the old Command & Conquer games [2] though interestingly left out Tiberian Sun and Red Alert 2, StarCraft's closest competitors at the time.
Would've been nice for historical preservation to be able to peek behind the curtain and see StarCraft's code in a similar fashion
[1] https://old.reddit.com/r/gamecollecting/comments/68xzxt/star...
The StarCraft source code is something that must be kept behind closed walls, under tight control by Blizzard, even though the original people working on the game at Blizzard have already left and there is nothing to protect here other than eternal shame.
Oh, you wouldn't want to, believe me. You'd be scarred by code like this:
class CUnit ... {
#include "header_1.h"
#include "header_2.h"
#include "header_3.h"
#include "header_4.h"
};
I never developed standalone demos -- I was already working so many hours at work there wasn't much left over for, y'know, regular things like having a life.
On a related note, I worked on Battle Chess, porting it from DOS/Amiga to Windows 3.1, and later to Windows 95 ("MPC Battle Chess"). Every few years a new producer from Interplay would call me and ask for a copy of the source code so they could rebuild it, because they lost their own copies. One of those times it was because they discovered their weekly backup tapes were all blank.
Numeric characteristics are absolutely still a consideration for game designers even in 2026, one that influences what numbers they use in their game designs. The good ones, anyways. There are, of course, also countless bad developers/designers who ignore these things these days, but not because it is free to do so; rather, because they don't know better, and in many cases it is one of many silent contributing factors to a noticeable decrease in the quality of their game.
I used to think like this, not anymore.
What convinced me that these sort of micro-optimizations just don't matter is reading up on the cycle count of modern processors.
One a Zen 5, Integer addition is a single cycle, multiplication 3, and division ~12. But that's not the full story. The CPU can have 5 inflight multiplications running simultaneously. It can have about 3 divisions running simultaneously.
Back in the day of RCT, there was much less pipelining. For the original pentium, a multiplication took 11 cycles, division could take upwards of 46 cycles. These were on CPUs with 100 Mhz clock cycles. So not only did it take more cycles to finish, couldn't be pipelined, the CPUs were also operating at 1/30th to 1/50th the cycle rate of common CPUs today.
And this isn't even touching on SIMD instructions.
Integer tricks and optimizations are pointless. Far more important than those in a modern game is memory layout. That's where the CPU is actually going to be burning most it's time. If you can create and do operations on a int[], you'll be MUCH faster than if you are doing operations against a Monster[]. A cache miss is going to mean anywhere from a 100 to 1000 cycle penalty. That blows out any sort of hit you take cutting your cycles from 3 to 1.
They’re not pointless; they’re just not the first thing to optimize.
It’s like worrying about cache locality when you have an inherently O(n^2) algorithm and could have a O(n log n) or O(n) one. Fix the biggest problem first.
Once your data layout is good and your cpu isn’t taking a 200 cycle lunch break to chase pointers, then you worry about cycle count and keeping the execution units fed.
That’s when integer tricks can matter. Depending on the micro arch, you may have twice as many execution units that can take integer instructions. And those instructions (outside of division) tend to have lower latency and higher throughput.
And if you’re doing SIMD, your integer SIMD instructions can be 2 or 4x higher throughput than float32 if you can use int16 / int8 data.
So it can very much matter. It’s just usually not the lowest hanging fruit.
For integers the situation is better but even there, it hugely depends on your compiler and how much it cheats. You can't replace trig with intrinsics in the general case (sets errno for example), inlining is at best an adequate heuristic which completely fails to take account what the hot path is unless you use PGO and keep it up to date.
I've managed to improve a game's worst case performance better by like 50% just by shrinking a method's codesize from 3000 bytes to 1500. Barely even touched the hot path there, keep in mind. Mostly due to icache usage.
The takeaway from this shouldn't be that "computers are fast and compilers are clever, no point optimising" but more that "you can afford not to optimise in many cases, computers are fast."
A good example of this is using std::vector<bool> vs. std::vector<uint8_t> in the debug build vs release build.
vector<bool> is much slower to access (it's a dynamic bitset). If you have a hot part of the code that frequently touches a vector<bool>, you'll see a multiple X slowdown in the debug build.
However, in the release build, there is no performance difference between the two (for me at least, I'm making a fairly complicated game). The cache misses bury it.
All possible numerical representations come with inherent trade-offs around speed, accuracy, storage size, complexity, and even the kinds of questions one can ask (it's often not meaningful to ask if two floats equal each other without an epsilon to account for floating point error, for instance).
"Toward an API for the Real Numbers" ( https://dl.acm.org/doi/epdf/10.1145/3385412.3386037 ) is one of the better papers I've found detailing a sort of staged complexity technique for dealing with this, in which most calculations are fast and always return (arbitrary precision calculations can sometimes go on forever or until memory runs out), but one can still ask for more precise answers which require more compute if required. But there are also other options entirely like interval arithmetic, symbolic algebra engines, etc.
One must understand the trade-offs else be bitten by them.
Today, I imagine we have conversations like this happening:
Game designer: We will have 300 different enemy types in the game.
Programmer: Things could be really, really faster if you could limit it to 256 types.
Game designer: ?????
That ????? is the sign of someone who is designing a computer program who doesn't understand the basics of computers.
Fumito Ueda was notably quite concerned with the technical/production feasibility of his designs for Shadow of the Colossus. [1] Doom was an exercise in both creativity and expertise.
[1] https://www.designroom.site/shadow-of-the-colossus-oral-hist...
And he didn't really achieve it - the game runs very slowly and has a good deal of cut content.
(I once got him in trouble because I found a GPL violation in ICO. I assume the developer didn't pursue it because I don't see the source code up anywhere.)
Game designers are not so constrained anymore by the limits of the hardware, unless they want to push boundaries. Quality of a game is not just the most efficient runtime performance - it is mainly a question if the game is fun to play. Do the mechanics work. Are there severe bugs. Is the story consistent and the characters relatable. Is something breaking immersion. So ... frequent stuttering because of bad programming is definitely a sign of low quality - but if it runs smooth on the targets audience hardware, improvements should be rather done elsewhere.
Texture resolution mismatches causing blurriness/aliasing, floating point errors and bad level design causing collision detection problems (getting stuck in the walls), frame rate and other update rates not being synced causing stutter and lag (and more collision detection problems), bad illumination parameters ruining the look they were going for, numeric overflow breaking everything, bad approximations of constants also breaking everything somewhere eventually, messy model mesh geometry causing glitches in texturing, lighting, animation, collision, etc.
There's probably a lot more I'm not thinking of. They have nothing to do "with the hardware", but the underlying math and logic.
They're also not bugs to "let the programmer figure out". Good programmers and designers work together to solve them. I could just as easily hate on the many criminally ugly, awkward, and plain unfun games made by programmers working alone, but I'll let someone else do that. :)
The thing that changed during the 90's is that mechanical sympathy became optional to achieving a large production. The data input defining the game world was decoupled into assets authored in disconnected ways and "crunched down" to optimized forms - scans, video, digital painting, 3D models. RCT exhibits some of this, too, in that it's using PCM audio samples and prerendered sprites. If the game weren't also a massive agent simulator it would be unremarkable in its era. But even at this time more complex scripting and treating gameplay code as another form of asset was becoming normalized in more genres.
From the POV of getting a desired effect and shipping product, it's irrelevant to engage with mechanical sympathy, but it turns out that it's a thing that players gradually unravel, appreciate and optimize their own play towards if they stick with it and play to competitive extremes, speedrun, mod, etc.
The 64kb FPS QUOD released earlier this year is a good example of what can happen by staying committed to this philosophy even today: the result isn't particularly ambitious as a game design, but it isn't purely a tech demo, nor does it feel entirely arbitrary, nor did it take an outrageous amount of time to make(about one year, according to the dev).
10000x this. Miyamoto starts with a rudimentary prototype and asks himself this. Sadly it seems for many fun is an afterthought they try to patch in somehow.
If your game is small-scale, something like Super Mario Bros., you should be able to get away with not thinking about it in theory. But even then people manage to write simple games with bloated loading times and stuttery performance, so never underestimate the impressive ability of people who are operating solely at the highest level of abstraction to make computers cry.
By not having to pull in anything from the constant pools and thereby avoid memory stalls in the fast path, we got to use random numbers profligately and still run quickly and efficiently, and get to sleep quickly and efficiently. It was a fun little piece of engineering. I'm not sure how much it mattered, but I enjoyed writing it. (I think I did most of it after hours either way.)
Alas, I don't think it ever shipped because we eventually moved to an even smaller and cheaper Cortex-M0 processor which lacked those instructions. Also my successor on that project threw most of it out and rewrote it, for reasons both good and bad.
Which wasn't a problem, but it clearly showed how the programmers improvised to make it perform.
Similarly, redstone has 16 power levels: 0 to 15. This allows it to store the power level using 4 bits. In fact, quite a lot of attributes in Minecraft blocks are squeezed into 4 bits. I think the system has grown to be more flexible these days, but I'm pretty sure the chunk data structure used to set aside 4 bits for every block for various metadata.
And of course, the world height used to be at 255 blocks. Every block's Y position could be expressed as an 8-bit integer.
A voxel game like that is a good example of where this kind of efficiency really matters since there's just so much data. A single 1616256 chunk is 65.5k blocks. If a game designer says they want to add a new light source with brightness level 20, or a new kind of redstone which can go 25 blocks, it might very well be the right choice to say no.
From what I heard, there was a Civilization game which suffered from an unsigned integer underflow error where Gandhi, whose aggression was set to 0, would become "less aggressive" due to some event in the game, but due to integer underflow, this would cause his aggression to go to 255, causing him to nuke the entire map.
The article says this was just an urban legend though. Well, real or not, it's a perfect example of the principle!
> I have calculated the value of Pi on Sausage Island and found it to be 2.
https://web.archive.org/web/20240405034314/https://twitter.c...
World of Warcraft (at least originally) encoded every item as an ID. To keep the database simple and small (given millions of players with many characters with lots of items): if you wanted to permanently enchant your item with an upgrade, that was represented essentially as a whole new item. The item was replaced with a different item (your item + enchant). Represented by a different ID. The ID was essentially a bitmask type thing.
This meant that it was baked into the underlying data structures and deep into the core game engine that you could never have more than one enchant at a time. It wasn't like there was a relational table linking what enchants an item in your character's inventory had.
The first expansion introduced "gems" which you could socket into items. This was basically 0-4 more enchants per item. The way they handled this was to just lengthen item Ids by a whole bunch to make all that bitmask room.
I might have gotten some of this wrong. It's been forever since I read all about these details. For a while I was obsessed with how they implemented WoW given the sheer scale of the game's player base 20 years ago.
Four instructions, in about eight chips.
By combining shifts and adds Keith Barr was able to devise all the different filter and delay coefficients for 63 different reverb programs (the 64th one was just dead passthrough).
(emphasis mine)
Not at all true. Assuming the types are such that >> is equivalent to /, modern compilers will implement division by a power of two as a shift every single time.
Looking at the macro-level optimizations like the rest of the article does is significantly more interesting.
> NewValue = OldValue >> 3; > This is basically the same as
> NewValue = OldValue / 8;
> RCT does this trick all the time, and even in its OpenRCT2 version, this syntax hasn’t been changed, since compilers won’t do this optimization for you.
The author loses a lot of credibility by suggesting the compiler won't replace multiplying or dividing by a factor of 2 with the equivalent bit shift. That's a trivial optimization that's always been done. I'm sure compilers were doing that in the 70s.
sar eax, 0x1f
and eax, 7
add eax, edx
sar eax, 3
And while this wouldn't apply to C++, in languages with checked arithmetic, the left shift won't necessarily set the overflow flag, so the compiler often can't use it.
"Interview with RollerCoaster Tycoon's Creator, Chris Sawyer (2024)" https://news.ycombinator.com/item?id=46130335
"Rollercoaster Tycoon (Or, MicroProse's Last Hurrah)" https://news.ycombinator.com/item?id=44758842
"RollerCoaster Tycoon at 25: 'It's mind-blowing how it inspired me'" https://news.ycombinator.com/item?id=39792034
"RollerCoaster Tycoon was the last of its kind [video]" https://news.ycombinator.com/item?id=42346463
"The Story of RollerCoaster Tycoon" https://www.youtube.com/watch?v=ts4BD8AqD9g
0: 55 push %bp
1: 8b ec mov %sp,%bp
3: 8b 46 04 mov 0x4(%bp),%ax
6: c1 e0 02 shl $0x2,%ax
9: eb 00 jmp 0xb
b: 5d pop %bp
c: c3 ret
int
main (int argc, char **argv)
{
return argc * 4;
}
For multiplying with powers of two greater or equal to 16, they use shift left, because LEA can no longer be used.
> RCT does this trick all the time, and even in its OpenRCT2 version, this syntax hasn’t been changed, since compilers won’t do this optimization for you.
At first this sounds like a strange technical obscurity"
Do we not know binary in 2026? Why is this a surprise to the intended audience?
> NewValue = OldValue << 2;
I disagree with the framing of this section. Bit shifts are used all the time in low-level code. They're not just some archaic optimisation, they're also a natural way of working with binary data (aka all data on a computer). Modern low-level code continues to use lots of bit shifts, bitwise operators, etc.
Low-level programming is absolutely crucial to performant games. Even if you're not doing low-level programming yourself, you're almost certainly using an engine or library that uses it extensively. I'm surprised an article about optimisation in gaming, of all things, would take the somewhat tired "in ye olde days" angle on low-level code.
dc->color=c++&15;
Hint: it's from this "Lines" demo program, whose source is here: https://web.archive.org/web/20180906060723/https://templeos....
And this is what it looks like when it runs (ignore the fact it's running in Minecraft): https://youtu.be/pAN_Fza6Vy8?t=38
I was reminded of the factorio blog. That game's such a huge optimization challenge even by today's standards and I believe works with the design.
One interesting thing I remember is if you have a long conveyor belt of 10,000 copper coils, you can basically simplify it to just be only the entry and exit tile are actually active. All the others don't actually have to move because nothing changes... As long as the belts are fully or uniformly saturated. So you avoid mechanics which would stop that.
He has lots of videos that are deep dives into how RCT works and how things are implemented!
The more I actually started digging into assembly, the more this task seems monumental and impossible.
I didn't know there was a fork and I'm excited to look into it
Now writing very optimized assembly is very hard. Because you need to break your consistency and conventions to squeeze out all the possible performance. The larger "kernel" you optimize the more pattern breaking code you need to keep in your head at a time.
I think it'd be cool to do assembler on a Pi Pico or something, that seems like it would be a fun exercise.
OpenRCT2 isn't a fork, it's like OpenTTD, a recreation.
Go look at GDC's Classic Game Postmortems. They have tens of videos of the people who built famous games from the 80s and 90s who often go into technical details of how they do it. For example, Robotron goes into how the code works.
It's remarkably familiar. They basically built object oriented programming and classes using convention only. You treat every actor you want to work with as a chunk of memory with standard layout that includes pointers for behavior and slots for state, and you just try really hard to only operate on the right "Types" at the right places. From there you have your standard game loop of "Get input, update all Actors, render, loop"
The Pitfall postmortem is wonderful. The Atari 2600 had roughly zero RAM to work with, and barely any cartridge space to hold your game. To make their large, somewhat open world, they made each screen built off just a few parameters, and created a bidirectional psuedorandomish function that would generate the parameters on a cycle, giving you a connected map space!
Not saying that it was not a huge feat, but it’s definitely a lot harder to start from scratch nowadays, even for the same platform.
But if you look at creative writing, story arcs are all about obstacles. A boring story is made interesting by an obstacle. It is what our protagonist needs to overcome. A one-man-band game dev who simultaneously holds the story and the technical challenge their head, might spot the opportunity to use a glitch or limitation as, I dunno, a mini game that riffs on the glitch.
Like no one who wrote any code back in the 80s or 90s even for a homebrew game was skipping this stuff, it was in almost every book and tutorial. Stuff like bit shifting was extremely common and a lot of games would have had design choices that were informed by coding challenges. Lots and lots of code had data structures aligned on byte/word boundaries or had data massaged to fit into the limits of hardware in order to make reads happen in a certain # of cycles, etc.. certainly almost all console games had lots and lots of fascinating design choices like this.
This game may have been exceptionally well optimized but it feels like if the original code is not in the public domain these weren't the best examples.
When he started writing about their being a clean sheet re-implementation I thought there was going to be a benchmark comparison of the modern rewrite vs the original on old hardware or something, that would have been interesting.
Thankfully or not I'm just barely young enough that I never had to write anything professional in assembly, though if I had gone into games maybe I would have.
For the lesson here, I think re-contextualizing the product design in order to ease development should be a core tenant of modern software engineering (or really any form of engineering). This is why we are usually saying that we need to shift left on problems, discussing the constraints up-front lets us inform designers how we might be able to tweak a few designs early in order to save big time on the calendar. All of the projects that I loved being a part of in my career did this well, all of the slogs were ones that employed a leadership-driven approach that amounted to waterfall.
Somehow even as a child I just knew that it would be a whole new emergent game play experience.
Ofcourse I didnt know waht went into making Rolelrcoaster Tycoon but I could just by a couple of screenshots how this was clearly a ground up new game with new mechanics that would be extremely fun to play.
I dont get this feeling anymore, as I just assyne everything is just a clone of another game in the same engine generally.
Unless its been a decade in production like Breath of the Wild of GTA 5 i just dont expect much.
It does make you wonder if the future of AI-assisted development will look more like the early days of coding, where one single mind can build and deliver a whole piece of software from beginning to end.
imul rdx, rdx, 1717986919
shr rdx, 32
sar edx
sar eax, 31
sub edx, eax
mov eax, edxReminds me of blood moons in Zelda https://www.polygon.com/legend-zelda-tears-kingdom/23834440/...
> NewValue = OldValue >> 3;
You need to be careful, because this doesn't work if the value is negative. A
The biggest caveat is that right shifting -1 still produces -1 instead of 0, but that's usually fine for much older game fixed-point maths since -1 is close enough to 0.
However, there is a quirk of the hardware of most CPUs that has been inherited by the C language and by other languages.
There are multiple ways of defining integer division when the dividend is not a multiple of the divisor, depending on the rounding rule used for the quotient.
The 2 most frequently used definitions is to have a positive remainder, which corresponds to rounding the quotient by using the floor function, and to have a remainder of the same sign with the quotient, which corresponds to rounding the quotient by truncation.
In most CPUs, the hardware is designed such that for signed integers the division instruction uses the second definition, while the right shift uses the first definition.
This means that when the dividend is a multiple of the divisor, division and right shift are the same, but otherwise the quotient may differ by one unit due to different rounding rules.
Because of this, compilers will not replace automatically divisions with right shifts, because there are operands where the result is different.
Nevertheless, the programmer can always replace a division by a power of two with a right shift. In all the programs that I have ever seen, either the rounding rule for the quotient does not matter or the desired definition for the division is the one with positive remainder, i.e. the definition implemented by right shift.
In those cases when the rounding rule matters, the worrisome case is when you must use division not when you can use right shift, so you must correct the result to correspond to rounding by floor, instead of the rounding by truncation provided by the hardware. For this, you must not use the "/" operator of the C language, but one of the "div" functions from "stdlib.h", or you may use "/" but divide the absolute values of the operands, after which you compute the correct signed results.
I really wish I could see the source code.
Surely it wasn't all assembly. There is little to be gained in performance from writing non-bottleneck parts of the code in assembly.
> It's 99% written in x86 assembler/machine code (yes, really!), with a small amount of C code used to interface to MS Windows and DirectX.
And this folks is why an optimizing compiler can never beat sufficient quantities of human optimization.
The human can decide when the abstraction layers should be deliberately broken for performance reasons. A compiler cannot do that.
… oh wait, nvm. Don’t preoptimize!
If AI has any benefit to creative endeavors at all it will be because of the challenges of coaxing a machine defined to produce an averaging of a large corpus of work (producing inherently mediocre slop) provides novel limitations, not because it makes art any more "accessible".