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In the game, 32-bit, little-endian ARM assembly instructions fall, and you can modify the operands before executing them on a CPU emulator. There are two segments mapped – one for instructions, and one for data (though both have read, write, and execute permissions). Your score is a four byte signed integer stored at the virtual address pointed to by the R12 register, and the goal is to use the instructions that fall to make the score value in memory as high as possible. When it's game over, you can download your game as an ELF to relive the glory in GDB on your favorite ARM device.
The CPU emulator is a version of Unicorn (https://www.unicorn-engine.org/) that has been cross-compiled to WebAssembly (https://alexaltea.github.io/unicorn.js/), so everything on the page runs in the browser without the need for any complicated infrastructure on the back end.
Since I've only been working on this for a short period of time leading up to its debut at DEF CON, there are still many more features I'd eventually like to implement. These include adding support for other ISAs besides ARM, adding an instruction reference manual, and lots of little cleanups, bug fixes, and adjustments.
My highest score is 509,644,979, but my average is about 131,378.
I look forward to feedback, bug reports, feature requests, and strategy discussions!
This is really cool! So far I have a high score of 65612 :)
Some feedback:
- When opening the help menu, it wasn't obvious how to close it (I think the only way is by pressing '?')
- I like the Goblin music!
- It's a pretty nice interface to play with the instructions and I appreciate the color coding. It would be neat if there was a "sandbox mode" where you could preview the effects of running an instruction, and maybe modify your program once the game is over. I could see this being pretty useful for someone learning ARM assembly.
I like the idea of sandbox mode!
I'm definitely much quicker at reading ARM assembly after playing a few hours of this game over the course of making it.
I'm computer literate (and know some basic assembly) but wow I did not get it
Hey, any specific questions? I'd be happy to explain anything that needs clarification.
More broadly, any thoughts on how to make the game clearer? I know that a manual describing the instructions would help. But other ideas are welcome as well!
Maybe a way to break down a game after it happened, or maybe a sandbox mode to try arbitrary things
I don't understand what "rotate the instruction order" keys do. I tried pressing them in many circumstances and nothing happens
Yeah, I may have sacrificed clarity for concision in this case.
To answer by way of example, if you are given "add R1, R2, R3" rotating to the right will result in "add R2, R3, R4". As another example, rotating "mov LR, R0" to the left will give "mov R12, SP".
In other words, rotating right changes every register RN in the instruction to be the register R(N + 1). Left changes RN to R(N - 1).
My hope was that if it was not clear from reading, it would be after testing things out. But hearing that this may not be the case is helpful feedback!
Oh, my bad, I misread your question.
See a reply to your original comment: it changes the order for gadgets larger than one instruction. The default is one, but originally it was three, so the instructions stuck.
I will make those confusing instructions only show up when the gadget size is greater than one! This feels like a good change to make based on this feedback.
Just figured it out. If you select "Adjust Difficulty" and increase the max gadget size (number of instructions that can fall at once) you change their order with these keys.
P.S. thank you for nerd sniping me with this game, I love the idea and execution (pun slightly intended)!
Thanks for the kind words! This comment helped me realize that I had misunderstood the parent commenter's question.
I have just pushed an update so that the up/down arrow keys only show up in the instructions if the max gadget size is greater than one.
i code frontend and backend web apps in javascript and typescript, very comfy with cloud stufd
but oh boy these assembly stuff these are heiroglyphs to me haha
You could add a puzzle mode with a fixed set of instructions introducing gameplay elements like rotate after a few puzzles to make it easier and more interesting to learn the game. My first play, I got a lot of sub instructions and my registers had all zero value. It was somehow partly pointless: Should I rotate and do sub R1, R2, R3 or do sub R2, R3, R4 to get a nop somewhere ? ;) XD
Very cool!
Beautiful brutalist ui/ux!
yeah... wanted to leave a comment I dig the aesthetics.
Nop is blue bar?
wow, you can even remap the keys!
It also works with USB gamepads!
At DEF CON where we will have this set up in-person tomorrow, we will have people playing on a USB Dance Dance Revolution floor pad.
Cool! Does that use the Gamepad API or WebHID? I'd like to get one working in the browser for one of my projects
Uses the Gamepad API. I found it very easy to work with, in large part thanks to the corresponding MDN docs.
The only weird part about the Gamepad API is that you have to poll it rather than handling events the way you normally would for other, similar stuff in JavaScript. In practice, this means that you have to do your own debouncing for handling things like key combos, but that doesn't really affect individual button presses too much.
Magic, thanks! Which model mat do you have?
It might be worth trying with WebHID instead of the GamePad API. Quick example with a joystick :)
https://murkle.github.io/utils/webhid/logitech_attack3.html
... and a quick example with a very cheap USB Dance Mat https://murkle.github.io/utils/webhid/dance_mat.html
What an amazing idea.
Another thing to make the entry easier: Create a "Memory" label for the memory area. You mention it in the intro text but color it in the R12 address color which was confusing for me.
Missed that memory space totally while playing the first two times.
ASM years ago. MOV'ing without any initial data feels unnerving. WASM and JupyterLite would be cool, too.
Category:Instruction_set_listings has x86 but no aarch64: https://en.wikipedia.org/wiki/Category:Instruction_set_listi...
/? jupyter asm [kernel]:
- "Introduction to Assembly Language Tutorial.ipynb" w/ the emu86 jupyter kernel which shows register state after ops: https://github.com/gcallah/Emu86/blob/master/kernels/Introdu...
- it looks like emu86 already also supports RISC, MIPS, and WASM but not yet ARM: https://github.com/gcallah/Emu86/blob/master/assembler/WASM/...
- DeepHorizons/iarm: https://github.com/DeepHorizons/iarm/blob/master/iarm_kernel... https://github.com/DeepHorizons/iarm/blob/master/iarm/arm_in... MOV https://github.com/DeepHorizons/iarm/blob/master/tests/iarm/... :
- JupyterLite > Adding other kernels; emu86, iarm, WASM, : https://jupyterlite.readthedocs.io/en/latest/howto/configure... [... https://github.com/jupyterlite/jupyterlite/discussions/968#d... ]
"Ask HN: How did you learn x86-64 assembly?" (2020) re: HLA, : https://news.ycombinator.com/item?id=23931373 re: the Diaphora bindiff tool and ghidra, which has GDB support now FWIU: https://news.ycombinator.com/item?id=36454485
As a programmer with practically 0 experience in working with assembly, this is a pretty cool tool to learn! I've been holding a cheatsheet in another tab to find out what each instruction is doing.
Kudos for building this, very cool!
edit: getting -4.8 billion as a high score because of my first segfault was... a disappointment, though. :-P
Before trying it I hit “About” and it opened a new page which says:
You seem to be in violation of the GDPR. There must be a way to refuse the cookies that is as simple as accepting them. Especially since yours are not needed for the site to function:
https://ofrak.com/privacy/#tracking-tools-and-opt-out
Telling people to delete cookies via their browser settings (further down that page) is not an acceptable solution.
Unfortunately this practice has been happening with a lot of websites, and many companies are not complaining with the cookie law
https://www.cnil.fr/en/refusing-cookies-should-be-easy-accep...
Not sure if it's an error from using autocorrect, but you probably want to use complying instead of complaining.
Telling site visitors to disable cookies via their browser is precisely how apple.com does it.
Even if Apple is in violation, that doesn’t make it acceptable or within the law. Big companies (notably Meta) frequently don’t comply with GDPR and are beginning to pay the price for it and making changes.
https://noyb.eu/en/5-years-litigation-meta-apparently-switch...
I was pleasantly surprised to see Apple’s cookie policy is considerably less intrusive than the submitted website’s.
https://www.apple.com/legal/privacy/en-ww/cookies/
GDPR doesn't care about cookies. It depends on what they're used for. If they're not used for tracking or storing personal information, GDPR doesn't apply.
It's easy to read the original comment as if you need to ask permission for any cookie usage. But that's not what they're saying. They're saying it applies for this site's cookies, as the site specify they use cookies in a way that GDPR would say you need consent for.
It's not even storing anything illegal on my end, only the game settings, so I don't know why it shows that banner.
Very cool concept, but my assembly understanding is really poor :)
It says that my score is stored in R12, but then why do I have a score of 16 of R12 is zero?
https://imgur.com/a/RY5jhTu
R12 contains the address of your score. In this case, that is address 0 - the start of the data segment.
The score register is yellow, and the corresponding memory region it points to (the actual bytes of your score) are also yellow.
Thank you, it makes sense now.
If you'd like to do a video tutorial how to play this well that could be a great resource to learn assembly intuitively.
This is so clever, I couldn't help but smile when I saw "Your score is stored in memory at the address pointed to by R12" :)
Thanks for sharing, it does makes me miss DEFCON, maybe next year...
Is the reason for R12 making you smile something you could share?
It's the fact that the score is handled within the game mechanics itself – so the way to get a high score is not just to play but to play with the goal of modifying R12 (so it points to a high value)
They could have easily made score be handled outside the game and you get a point per every executed statement within the time limit etc – but that would not be as fun
As someone who has very little idea of what instructions or addresses are, what is this a reference to?
Edit: I had the page loaded before your reply, so I didn't see it until I replied, reloading the page lol
It's not a reference, it's just a really neat game mechanic. Normally the high score is guarded by the game and changes only if the game deems it fit to change it. In this game, because the high score is accessible within the game and you can execute arbitrary instructions, you can use that to modify the high score.
It's as if in a more normal game the high score was kept in a big chest somewhere in the game world and once discovered you can start messing with the contents of it all within the rules of the world itself.
That game is Zelda on N64
https://www.zeldaspeedruns.com/oot/tech/get-item-manipulatio...
https://www.zeldaspeedruns.com/oot/ba/reverse-bottle-adventu...
Showing the next instruction would be helpful.
So far, I've used two good strategies:
- Spray PC into as many registers as possible, try to add those registers together as many times as possible, and store the sum at zero (or wherever the score ends up)
- Load an assembled instruction from an old value of PC as an int into a register, then do some subtraction to make it non-negative (since it's usually negative in my experience), then store in the score location
I'm curious what other strategies people have tried?
I've had a lot of success segfaulting the game, as I don't know any assembly.
This is just amazing :) kudos!
Peak nerddom - awesome.
I really like the concept!
The key to achieve high scores seems to be writing 0 to PC. The reason is the binary code of new instructions will be "added" to the memory region that is visible on the right, then we can manipulate R12 to maximize the score.
Ah, another key is to change R12 to a number that is not divisible by 4. This is because every instruction is 4 bytes and the most significant bit is always 1.
I got around 2 billon a couple of times but the average is quite low ;)
Trying to figure it out, I got 552 Million :)
Great concept! I'm afraid to show it to my team of C++ developers bc they might be tempted to switch over to doing everything in Assembly :)
My score is -50100627
omg, this is awesome. i’d been meaning to pick up some ARM assembly. and the fact that you managed to link game mechanics with working opcodes is great.
love it!
Very interesting game! Do you have any plans to make the RISC-V version? Thank you for sharing this game!
How to build the game?
I tried navigating https://ofrak.com/docs/environment-setup.html, but couldn't find anything specific about the tetris games. Perhaps I miss that?