Faultfinder (demo)
Wishlist Faultfinder on Steam · Full game Q4 2026 · This demo is also on Steam from 9 September
The engineer who kept the city aloft is dead, and her program is still running.
You have her listing, a machine whose registers, memory and ports you can watch, and a recorded execution trace of everything it did. Step through it, set breakpoints, rewind. Work out which single line killed her. Then name that line, and prove it.
A deduction game where the crime scene is a program.
What this is
You never write code. There is nothing to type. The program is already written, by a woman who is dead, and the whole game is reading it.
Fourteen runes. Six registers, a memory grid and three ports, all visible. A trace of hundreds of ticks you can scrub back through at will. Every case has exactly one answer, and it is machine-proven before it ships.
The demo
Seven cases, 35 to 70 minutes depending on how carefully you read. The first case is guided, eleven short cards that make you use the runes rather than read about them. the next six are not.
This is the same demo that goes live on Steam on 9 September for Programming Fest. Nothing here is missing from there.
Controls
Keyboard. Click the game once before pressing anything, or the browser will not send it your keys.
- SPACE step forward · B step back
- R run to the next breakpoint · END run the tape out · HOME back to the start
- Click a line to name it · click a chip to name the fault · click a teal cell on a strip to name the moment
- ESC back to the case book · I the readings panel, to inject a different gauge reading and run it again
- Every key's name on the bottom line can be clicked instead of pressed
Text too small? Settings has three sizes and a high-contrast mode.
Why it is here four days early
I want to know whether the first case teaches you enough to attempt the second without looking anything up. It is the part I have rewritten most and trust least. If it lost you, tell me where in the comments, and it will be fixed in the Steam build before the fest opens.
Why I made it
I started my career about 26 years ago writing C for the network processors in backbone routers. A lot of that job was debugging at the assembler level: reading a listing, watching registers, finding the one instruction that was wrong. It always felt like detective work to me. This is the detective game that is actually about that.
Wishlist on Steam · Endpaper Games · Godot 4 · Windows at launch
Development log
Comments
Log in with itch.io to leave a comment.
It looks like an interesting game but i cant full enjoy it as i am stuck on the tutorial level. On the level description i see underlined "the alarm bell never rang." and also "bell at or above twelve", the reading is 130 (13.0) > 12 which mean it should rang. After tracing i think the error is on line 20 'JMP 23' which skips past 'DRIVE BELL R3' command so it should be 'JMP 22', but i dont see how i would put this answer on the form to the right. Tried a lot of combinations but none worked.
You have solved it. The part you are missing is the game's fault, not yours, spoiler-safe underneath, ROT13 like the thread below:
Yvar 20 vf evtug, naq "WZC 23 fubhyq or WZC 22" vf rknpgyl jung gur tnzr pnyyf na bss-ol-bar obhaqnel. Gjb bs gur guerr pynhfrf ner nyernql lbhef.
Gur guveq nfxf jurer gur unez SVEFG FUBJF VA GUR ZNPUVAR, juvpu vf abg gur fnzr nf jurer lbh sryg vg. Lbh ner uhagvat gur oryy, naq gur oryy arire zbirq, fb vg unf ab fgevc gb pyvpx. Jung qvq zbir vf gur gncr urnq: gur gbc fgevc va gur onaq, juvpu znexf rirel whzc. Pyvpx gur pryy jurer pbageby tbrf fbzrjurer vg fubhyq abg.
The build going to Steam on Wednesday makes the strips say what they are for and the record stop pointing you at a target you cannot name. Thank you for writing it up, it is the most valuable bug report I could have had this weekend.
I enjoyed playing the first two cases; the logic and potential scope of the game is interesting and a new take on the detective genre
As a new user there were some hurdles, however, the jump between Case 1 & 2 was not an issue
The initial tutorial into Case 1, and the end of Case 2 had more of an issue for me
Discussion of Answer to Case 2: ROT13
Qrfcvgr fbyivat pnfr gjb gur vagraqrq Frny vachgf jrer abg pyrne
Sbe yvarf friragrra/rvtugrra, gur fjnc orgjrra ertvfgref bar naq gjb pbhyq unir orra vagrecergrq nf na bss ol bar obhaqnel reebe vafgrnq bs na havavgvnyvfrq ertvfgre reebe. Cyhf, vg jnf hapyrne juvpu bs gur gjb yvarf pbhagrq nf univat gur snhyg. Gur qvfgvapgvba jnf zber nobhg pbqr pbafvfgrapl engure guna pbqr ybtvp. Tvira gur nyy be abguvat inyvqngvba flfgrz vg jnf zber bs na vffhr
Zber rkcyvpvg obhaqnevrf ba pynff qrsvavgvbaf naq Svefg Unez pbhyq vzcebir guvf
For the tutorial/opening of cases
The tutorial skipped forward too easily since going back required restarting the tutorial
It has all the necessary detail buried in it, but not in the most accessible format
Rich text here would help with readability to highlight keywords e.g. keybings & selectables
Each case needs to start with the Context/Situation
Emphasise the top right box - perhaps start each case with a duplicate of it as a centre popup or similarly highlight when starting new
Similarly, this could use rich text formatting to highlight the core issue/keywords
There were a few other potential UX improvements
Easier method of skipping to specific line in The Listing - e.g. either double click or with breakpoints have pressing R skip to head when selecting the final line
Option to remove selections from The Seal more easily
Option for switching keybinds would help - especially for home/end
Tutorial box didn't block raycast causing selection of memory behind the box when clicked on
Highlighting of what can be selected in The Machine - perhaps a soft outline fade in when hover over
Would be useful if Flag/Tape Head/Clock also have a highlight when selected
Selection for Memory has outline same colour as fill - making these two states more distinct would increase clarity
This is the most useful thing anyone has sent me about this game, thank you.
The seal ambiguity is a real one, although the uniqueness of a case is machine-proven before it ships, what that proves is that no other repair explains the trace. It does not prove that the six class names carry boundaries clear enough to pick between, and your two readings of that swap are both defensible from the listing. Explicit definitions for the six, and for First Harm, are going in before the Steam build on Wednesday.
The tutorial is even worse than you found: any key advances it, and the back key skips the whole thing. That is why you could not go back. A back step and a deliberate skip are going in too, along with the machine showing what can be clicked, which I suspect is half of why the seal felt unclear.
Thanks again, great feedback.
You're more than welcome.
I'd also want to thank you, both for creating this game, but also for taking what I said in good faith.
I love a good puzzle, anything that helps keep the focus on solving it is a win for me.