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+# The big rewrite
+
+Recently I have been working on [nissy](https://nissy.tronto.net),
+my command-line Rubik's cube solver. But things were not going the
+way I wanted. I was trying to implement some minor but rather complex
+optimizations. It was a challenging problem and I made some good progress,
+but coming back to my code after not looking at it for weeks made it
+hard to debug it.
+
+I could work on this project more often. I rarely have long hours or days
+in a row to spend on it, but I do have some free time here and there -
+I write somewhat regularly in this blog, after all. So why was I not
+spending some more time on this project that I like so much?
+
+I think I was trying to do too much. I was trying to write this complex
+optimization for the puzzle-solving logic basically to prove to myself
+that I am capable of it, but at the same time I wanted to keep the
+tool usable for the few people interested in it. As new ideas piled up,
+I rushed through my code changes. Code quality degraded, and I was not
+improving the tool.
+
+It was time for...
+[the big rewrite](https://dylanbeattie.net/songs/big_rewrite.html)!
+
+## What is nissy?
+
+Nissy is a command line Rubik's cube solver and
+*[fewest moves](https://www.speedsolving.com/wiki/index.php?title=Fewest_Moves_Challenge)*
+solving assistant. You can find it's source code on its
+[git page](https://git.tronto.net/nissy).
+As a cube solver it is quite fast, faster than the classic
+[Cube explorer](http://kociemba.org/download.htm), although it uses
+much more RAM. But there is room for improvement.
+Additional features related to
+[Thistlethwaite's algorithm](https://en.wikipedia.org/wiki/Optimal_solutions_for_Rubik%27s_Cube#Thistlethwaite's_algorithm)
+make it useful tool for a certain niche of speedcubers. Although
+these features are appreaciated by nissy's users, the CLI interface
+and general usability is not as well-received.
+
+I started working on it in 2019, and after a few months of I had something
+we could call useful, at least for me. As I added more features and tried
+to implement a faster optimal solver, I noticed that I could make some
+improvements to its design. So I decided to rewrite nissy from scratch.
+
+"Rewriting from scratch" is a bit of a taboo among programmers.  It is
+exciting to start working on a new or "rebooted" project, but it is
+usually more time-efficient to just fix the old code.  Nonetheless,
+starting over worked for me: at the end of 2021 nissy was much faster,
+and more useful for everyone.
+
+Fast-forward another year or so, and I was at the point I described in
+the first paragraph. Since stopping to think, redesign and rewrite worked
+for this project last time, I decided to do this again.  I did not start
+nissy with a clear goal in mind, so it makes sense that I come up with
+better goals and design ideas as I go.
+
+## Setting a goal
+
+Nissy has been my pet project for the last 3.5 years or so.  I started
+writing because I wanted to see if I could do it, and decided which
+features to include along the way.  I have never had a precise goal for
+it, so I had to think about what I wanted nissy to be.
+
+Right now, nissy's most important features for its users (including
+myself) are:
+
+* Analyzing a "fewest moves" solution, helping the (human) solver spot
+  mistakes, oversigths and more advanced tricks that they missed.
+* Solving a Rubik's cube optimally, fast.
+
+The first part is basically already implemented, though some improvements
+can be made and some simple features can be added.  Most importantly,
+the interface should be made more accessible to people not familiar with
+the command line - more on this later.
+
+For the second part, the interface is less important, and I can expect the
+users to be able to learn how to launch one single command.  It is also
+the part that I find most interesting to work on, since the optimization
+problem is much more challenging.  On the other hand, the optimal solver
+implemented in the current version of nissy is already good enough for
+most users.
+
+Once I had written down these two main features, I realized that
+I would be much happier working on this project if I just stuck to
+those two things. And since *one* program should do *one* thing, I
+decided to split the two features into separate projects.  Any other
+cool idea I thought of implementing (a speed-solving assitant? a
+higher-order cube optimal solver? a generic, hackable puzzle solver like
+[ksolve+](https://mzrg.com/rubik/ksolve+)?)  is deferred to future
+projects, or probably it will be never done. And that's OK.
+
+## New plan
+
+My plan is to split the work into the following parts:
+
+* Starting from the [stable branch](https://nissy.tronto.net/download)
+  of nissy, remove all the code that is needed only by the optimal
+  solver and other unnecessary steps. Work on a GUI and other simple
+  features useful for assisting fewest moves solvers.
+* Branch off the optimal solver from the current
+  [working branch](https://git.tronto.net/nissy/) of nissy. Remove
+  all the code that is not needed for the optimal solver and simplify
+  the logic, where possible, to address only this use case.
+  Finish implementing the solver, basically following Tomas Rokicki's
+  [nxopt](https://github.com/rokicki/cube20src/blob/master/nxopt.md),
+  or at least parts of it.
+
+For the user interface, I have been thinking about what would be
+the best library / framework / technology to use. I would like
+this to be as accessible as possible, so I have been considering
+[WebAssembly](https://webassembly.org) so that people can just run this
+in their browser. But apparently a WebAssembly app needs an http server
+to work. I don't want nissy to require an internet connection, and
+shipping a whole web server to run locally with it is overkill. I have
+also been thinking about [Flutter](https://flutter.dev), it supports all
+majow platforms and has the C language as a first-class citizen.  I think
+I'll try making some proof of concept app with it and see how it goes.
+
+## A GUI app? Is this an April fools' joke?
+
+Am I a big fan of command line interfaces. I am such a fan of the command
+line that I dislike TUIs (such as
+[ncurses](https://en.wikipedia.org/wiki/Ncurses)-based programs), because 
+they are just GUIs running in a terminal.  So why am I even considering
+ruining my favourite personal project by adding a GUI?
+
+One reason is that I don't expect my (very few) users to be familiar with
+the command line. But this is not the main reason. I truly believe that,
+for this specific use case, a graphical user interface would be better.
+And it is not even a matter of showing a graphical representation of
+the cube - my users don't need it,
+[Singmaster notation](https://www.speedsolving.com/wiki/index.php/Singmaster_notation)
+is enough for them.
+
+The point is that this program is supposed to show you a bunch of
+information. The user might want to see more details, less details,
+group this information in different ways and so on. This information
+should be browsable. The user should, ideally, be able to follow a
+solution path proposed by nissy by simply selecting the suggested steps.
+
+This could all be done with commands, of course. But it would not be
+efficient. The command line is great when you know what information
+you want and you ask the computer to generate it or fetch it.
+But for interactively browsing information, especially when you do
+not know exactly what you are looking for, a GUI is better.
+
+## Ok, so when is it going be ready?
+
+Ah-ah. It will be ready when it's ready, no promises :)
diff --git a/src/blog/blog.md b/src/blog/blog.md
index 8589429..88c8e8b 100644
--- a/src/blog/blog.md
+++ b/src/blog/blog.md
@@ -5,6 +5,7 @@
 
 ## 2023
 
+* 2023-04-10 [The big rewrite](2023-04-10-the-big-rewrite)
 * 2023-03-30 [The man page reading club: dc(1)](2023-03-30-dc)
 * 2023-03-06 [Resizing my website's pictures with ImageMagick and find(1)](2023-03-06-resize-pictures)
 * 2023-02-25 [Job control: one shell is all you need](2023-02-25-job-control)
diff --git a/src/blog/feed.xml b/src/blog/feed.xml
index be949e6..c4fb4d9 100644
--- a/src/blog/feed.xml
+++ b/src/blog/feed.xml
@@ -9,6 +9,13 @@ Thoughts about software, computers and whatever I feel like sharing
 </description>
 
 <item>
+<title>The big rewrite</title>
+<link>https://sebastiano.tronto.net/blog/2023-04-10-the-big-rewrite</link>
+<description>The big rewrite</description>
+<pubDate>2023-04-10</pubDate>
+</item>
+
+<item>
 <title>The man page reading club: dc(1)</title>
 <link>https://sebastiano.tronto.net/blog/2023-03-30-dc</link>
 <description>The man page reading club: dc(1)</description>