The design system
Everything this site is made of, drawn by the same code that draws the site. If it is not here, it is not part of the system yet.
Principles
- One anatomy on every page: header, page head, body with a margin, page foot, footer.
- Content is the only variable. Places differ in what they hold, never in where things go.
- Everything is an entry with an address: place, kind, date and slug give one permanent URL and one row.
- Visuals carry meaning: every mark is real or explains something real.
- Paper and three pigments: ink, indigo, maroon. One pigment per element; two never mix.
- Fraunces for titles, Figtree to read, JetBrains Mono for labels; Tamil is first-class.
- Nothing overlaps. No counts, no streaks. No em dashes. Works without JavaScript, on a phone, at night.
Colour · day
paper#fefdfathe groundink#141416text, ink linesink-2#3a3a40secondary text, graphitemuted#6b6b72meta, labelsrule#e6e4dfhairlinesfield#f4f3efcode, quiet panelsmaroon#7a1f2ethe one point: seal, result, stateindigo#2a3a7cwhat matters: links, the washColour · night
paper#0f1019ink#f1efe9ink-2#c9c7c2muted#9a99a3rule#2a2c38field#171925maroon#e07f8cindigo#9aa8f0Type
nameFraunces 3.1remPrabakaran Chandranh1 · titleFraunces 2.6remWhy does a network forget?h2 · sectionFraunces 1.6remWhat happenedledeFigtree 1.28remOne sentence saying what this is.bodyFigtree 1.125rem / 1.62I chose control engineering somewhat by accident, and have looked at the world as a system ever since.metaJetBrains Mono .78rem17 Oct 2026 · log · workingquoteFraunces 1.06remGet the essence, and express it in your own style.TamilCatamaran · Noto Serif Tamilபிரபாகரன் சந்திரன் கற்க கசடறக் கற்பவைSpace
4px8px12px16px24px32px48px64px96pxGrid
The order of making
Marks happen in the order a hand makes them, and each medium keeps to its job, its pigment and its place. Every engine, scene, collection and diagram is on the visual library.
- 1Pencil · graphitethinking: construction lines, notes and arrows on figuresfigures, margins
- 2Ink · sumi blackdeciding: the line that is true, the data, the ensōfigures, inquiries, branches and birds
- 3Wash · indigowhat matters: a range, a region, a term, a skyfigures, covers, sparingly
- 4Charcoal, crayon, oil pastel · one pigment per markwarmth and play: sketches and personal piecesMusings, the sketchbook
- 5Kolam · ink line on paperthe threshold, drawn fresh each daythe front door only
- 6Hanko · maroonsigning: the theme switch, and the stamp on a settled piecethe header, the end of a piece
Places
/writing/WritingEssays on what I study and build, and musings on everything else: reflections, poems in English and Tamil, and the sketchbook.essay · reflection · poem · dialogue · sketch/lab/LabExperiments, notebooks and builds. Each one starts from a question, and its failures stay in the book.log · build · study · notebook · day · model · dataset/lessons/LessonsBentos of ten essential readings, courses I work through in the open, tutorials and primers from first principles, and the shelf I read from. Written so the next person gets there faster.bento · course · session · track · primer · tutorial · note · reading/inquiries/InquiriesWhat I keep asking, what I think now and how sure I am, and the work beneath each one. Answers welcome.inquiry/correspondence/CorrespondenceWhen an experiment changes my mind, I write a letter about it. There is no schedule, and each one asks you something back.letter
Components
G1 Header wordmark, places, the seal; the same on every page
At the top of this page.
G2 Footer contact, the record, elsewhere, the name line
At the foot of this page.
G3 Icons small marks on the things you click; one stroke in the text colour, or a service's own glyph
P1 Breadcrumb where this sits
P2 Page head title and one sentence
Causal State-Space Models for Time Series
Forecasting models predict what will happen — but decisions change the pattern. This integrates causal structure into sequence models so they can reason about interventions, not just correlations.
P3 Meta line date · kind · stage · modes
L1 Row the one list pattern
- Causal State-Space Models for Time Seriesbuildscience · engineering
- Daybook, 9 July 2026dayengineering
- Daybook, 10 July 2026dayscience · engineering
E7 Ensō on an inquiry's own page: the gap is how settled it is
E1 Frame the kind's summary in one place
E2 Figure numbered, captioned, in the house palette
E5 Quote their own sentences, with the source
Get the essence and express it in my own style.
from The Artist and the Engineer, 2026
E6 Outcome a labelled result line in the Lab
failed The invariance penalty hurt every head.
E8 Code highlighted at build time, three pigments, a copy button
def forget_less(features, classes):
# one covariance, pooled over every class seen so far
mu = {k: features[classes == k].mean(0) for k in set(classes)}
return mu, shrink(cov(features))E9 Artwork an open-access work, shown whole and credited

F1 Reply the end of every piece
If this was yours too, I'd like to hear it. Write to mepc3197@columbia.edu · the title goes in the subject line
F6 Share a small Share by the date; copy the link, or send it on, at the foot
F4 Letter line one input, one button, one promise
C6 Settled stamp the seal at the end of a settled piece
Settled · 27 Mar 2026
Where things live
site.jsonidentity, places, shelves, frames, the nav: the one configcontent/a piece; or content/<place>/<slug>/index.md with its figures beside it/ .md content/_data/art.json (credits for open-access works) and art-assign.json (which work stands in for which piece)design/tokens.cssevery colour, family, size and spacedesign/components/one file per component, named as on this page.css art/the mark-making engines: sumi (ensō, seal, ink), kolam, wash (watercolour, pencil), dry media, gardenfigures/the house kit for technical figures: matplotlib style, TikZ preamble, rulespress/the build: content → components → layouts → pagesstatic/fonts, vendored libraries, open-access imageslegacy/the old site, served unchanged until each page is portedtools/new.py (start a piece), check.py (links, devices), art.py (fetch an open-access work)