Slack water, posted like a harbour notice

1. client01

   /genjutsu:paint build the landing page for Étale.

   The brief. Étale is a fictional product, made up for this example, and this is everything we, its founders, have:

   • Étale is an iPhone app for people who swim in the cold water of Aquatic Park, San Francisco, all year round. It answers one question before you walk down to the beach: when is the water slack (étale is the French word for slack water, the still moment between ebb and flood, when the current is weakest), and how strong the current runs between two slacks.
   • Its numbers come from two NOAA CO-OPS stations, and data/tide.json holds one real day of both, 2 October 2026, as fetched from NOAA: the tide predictions of station 9414290 San Francisco, and the slack water and current predictions of station SFB1204 (Alcatraz Island, southwest of, the closest predicted current station, in the bay off the cove). The file names each station, where it is, its datum and its units. Use those numbers and label each one with its date and its station. Slack water is not high or low tide: take the slack times from the current predictions. The app shows no water temperature, so the page must not either. Do not invent any other figure.
   • The swimmers it is for train there before work, mostly without a wetsuit. They already know the cove and read the tide themselves on a printed table or a weather site. They want the next slack window at a glance, and an alert the evening before.
   • What exists: an iOS beta on TestFlight. No Android, no web app, no prices, no user numbers, no testimonials. The page has one job: get a swimmer onto the TestFlight beta, at /beta.

2. genjutsu01

   Scanning the ground before the first brushstroke.

   Scan done: React 19 + Vite + TypeScript, plain CSS, no animation library, no existing visual identity (index.css is a reset, App.tsx renders an empty <main />). data/tide.json has the full day for 2 October 2026: the 9414290 tide curve at 6-minute steps, two highs and two lows, and three slacks plus four current maxima at SFB1204 (05:57, 10:31 and 16:17 PDT, with a 2.11 kn ebb at 19:50).

   It’s one landing page, not a multi-page site, so I’ll use this pipeline rather than bunshin. With no existing design, there’s no preserve-or-redesign question.

   My read so far: a one-page TestFlight signup for Étale, an iPhone app that tells year-round, mostly no-wetsuit swimmers at Aquatic Park when the next slack water is and how hard the current runs between slacks. The readers already read tide tables and want the answer before they walk down to the beach. The direction I’m leaning toward is quiet, exact and set around the data: the real 2 October slack times as the main element, with every figure labelled by date and station, and no temperature or invented numbers. Stack: React + Vite + plain CSS, no animation library.

   Correct me before I ask anything.

3. client02

   That’s right. One more thing: the alert the evening before matters as much as the slack window, so don’t leave it out.

4. genjutsu02

   Noted: the evening-before alert gets as much weight as the slack window. It won’t be a footnote.

   First question, about mood. You know these swimmers and I don’t: at the moment they check Étale (dark, early, cold, before work), what should the page feel like, and what would feel wrong for them? For example, does a bright, sporty, “crush your swim” tone grate on them? Or is it something quieter, like a harbour notice or a printed tide table? Three to five words, or one thing they’d roll their eyes at, would be enough.

5. client03

   Quiet, grey, exact, a bit early-morning. Like a harbour notice or the printed table on the club noticeboard. They’d roll their eyes at anything bright and sporty, or anything that sells cold water as toughness.

6. genjutsu03

   “Quiet, grey, exact” settles the tone. Here’s the one fork your answer leaves open, and it decides the whole palette:

   Should the page be light or dark? The harbour notice and the club table point to a light grey printed sheet: dark ink on a cool, flat grey, like a posted notice. “Early morning before work” points to a dark screen read before dawn, with grey-blue ink on near-black, the way a phone looks at 5:30. Both can be quiet and exact. They just feel like different objects. Which one is closer to how your swimmers actually meet the information: the noticeboard, or the phone in the dark hallway?

7. client04

   The phone in the dark hallway. That’s when they actually check it, and the alert the evening before also comes in on a dark screen. Keep it grey and quiet though, not black and glossy.

8. genjutsu04

   That gives me enough to write both theses: a dark, grey, quiet page built for reading in a dark hallway, laid out like a posted notice, with the slack window and the evening alert carrying equal weight.

   Before I show them, how do you want to see them?

   • A. Rendered page (recommended: a whole visual identity is at stake). A throwaway HTML file with the swatches and their contrast ratios, a type specimen, the easing curve plotted, and a slack card and an alert preview that actually move. This session can’t open a browser, so I’ll give you the file path to open.
   • B. Live preview. A throwaway route inside this Vite project, using the real stack. It needs npm run dev, which I won’t start without asking.
   • C. Inline. The two theses written out here in text.

9. client05

   A, the rendered page. Please save each preview as a standalone HTML file in a preview/ folder in the project so I can open it.

10. genjutsu05

    Painting the preview: palette, type and the slack chart, all on a dark grey ground. First, checking contrast and the day of the week.

    Visual thesis: a dark, cool-grey notice read on a phone in a dark hallway. The ground is flat slate (#1A1E21), the ink comes in three greys, and there’s one pale sea-glass accent (#A9CCC5) used only for slack water and the beta button. The typeface is Public Sans, the US federal web typeface, because it has the plain tone of a posted harbour notice and its figures line up in columns of times. Large numbers sit against small labels. Spacing is unhurried, but the data is set as tight as a printed tide table. Components are flat and sharp: 2px corners, 1px hairline rules, no shadows.

    Interaction thesis: still, like slack water. Elements fade in and rise 8px over 480ms on one easing curve, cubic-bezier(0.32, 0, 0.16, 1), 80ms apart, and play once on load. The current line draws once over 1200ms. Hover changes colour only, in 160ms. Nothing is tied to scroll. Forbidden: bounce, parallax, scroll reveals, looping animation, numbers that count up, anything sporty or heroic.

    Allowed patterns: hairline rules, small uppercase source labels under each figure, figures that line up in columns, a chart of the real SFB1204 current predictions, and the evening alert drawn in HTML as a notification, labelled as an illustration.

    The preview below shows the proposal, not the build:

    preview/thesis.html. This session’s sandbox can’t open a browser, so run open preview/thesis.html yourself. It has:

    • the easing curve plotted, with Replay and Reduced-motion buttons;
    • one real slack card and the evening alert, side by side and at equal size;
    • the SFB1204 current chart for 2 October 2026. The dots are NOAA’s predicted slacks and maximums, and the lines between them are labelled as a reading aid, not as predictions;
    • the swatches with their computed contrast ratios, the type scale, the spacing steps and the corner radii.

    Every figure comes from data/tide.json and carries its date and station. There’s no water temperature.

    Do both theses hold, as written? Or should anything change: the accent, the typeface, or how much motion there is?

11. client06

    Both hold. It reads like our water: slack times from SFB1204, the source under every figure, the alert next to the slack card, and nothing sporty. Keep the accent, the typeface and the motion as they are.

12. genjutsu06

    Both theses validated. Loading tells before the design-system query.

    tells loaded. Running the design-system query with the validated thesis.

    Design-system query done. Writing MASTER.md and the tokens.

    Rendering the design-system preview.

    The design system is ready, on a rendered page in the same mode as before.

    preview/design-system.html: open it with open preview/design-system.html. It shows every token group, the button and text link in all five states (default, hover, focus, pressed, disabled), the card with its data rows and source line, the notification, and the motion settings with a Replay button. It’s a throwaway page; the real build will read the tokens from MASTER.md.

    Files written

    • MASTER.md: the full design system, with both validated theses and the content rules from your brief.
    • src/tokens.css: the same values as CSS variables. Nothing uses them yet.

    What I took from the design-system lookup, and what I dropped

    • Kept: its standard checks (tap targets of at least 44px, visible focus, reduced motion, testing at 375 to 1440px wide) and short colour-only hover changes.
    • Dropped the palette: navy and gold, on a light background. It contradicts the dark grey thesis.
    • Dropped the type: Inter at weight 900 with oversized text. That’s a reflex choice; Public Sans stays.
    • Dropped the “app store” page layout: star ratings, a screenshot carousel and a Play Store button. All three would be invented: you have no ratings, no screenshots and no Android app.
    • Dropped the GSAP motion code: I only read it for timing, and installed nothing.

    Lookup settings, and where each value came from

    • Layout boldness 3: from “flat and sharp… a posted harbour notice”.
    • Motion 2: from “played once on load… nothing tied to scroll”.
    • Density: not sent. The thesis pulls both ways (“unhurried” spacing, data “tight like a printed tide table”), so I set the spacing by hand.

    Three things the page could pass off as decoration, all deliberate and listed in your allowed patterns:

    • a thin rule on every data row;
    • small uppercase source labels;
    • the notification drawn in HTML, labelled as an illustration.

    Two small additions to what you saw in the first preview

    • The big slack time now grows to 4rem on wide screens; it was fixed at 3.5rem.
    • I left out colours for success, warning and error, because the page has no form and nothing to report.

    The font loads from Google Fonts through a <link> tag. No npm package gets installed.

    Is this design system right to build the page from? If so, I’ll build the hero next (heading, slack card, alert and beta button) and show it to you before the chart and the rest of the page.

13. client07

    Yes, build from it. Go ahead with the hero.

14. genjutsu07

    Loading the implementation modules, one per call.

    Building the hero: page heading, slack card, evening alert and the beta button.

    Now the styles, all read from the tokens.

    The hero is built and npm run build passes, with type-checking and the Vite build both clean.

    What it shows

    • Header: the “Étale” wordmark and “iPhone app · TestFlight beta”.
    • Heading: “Slack water off Aquatic Park, before you walk down to the beach.” It says “off” rather than “at” because neither NOAA station is in the cove itself.
    • Intro: one paragraph on what the app answers, then the definition of étale.
    • Slack card: “Slack water, Friday 2 October 2026”, with 05:57 PDT in the accent colour. Below it, the rest of the day: ebb strongest 0.94 kn at 08:06, next slack 10:31, flood strongest 1.44 kn at 13:37, next slack 16:17, ebb strongest 2.11 kn at 19:50. A line underneath names station SFB1204, where it is, and the date.
    • “The evening before”: sits beside the card, with its own heading and one sentence. Under them is the notification (“Tomorrow, Friday 2 Oct: slack at 05:57 / Then the ebb builds to 0.94 kn by 08:06. SFB1204.”) with a caption saying it’s an illustration using the SFB1204 predictions for 2 October 2026.
    • Button: “Join the TestFlight beta”, linking to /beta, with “iPhone only, through Apple’s TestFlight.”

    How it’s built

    • Every figure is read from data/tide.json in src/tide.ts; none are typed into the page.
    • The slacks come from the SFB1204 current predictions only. There’s no water temperature.
    • On load, elements fade in and rise 8px over 480ms, 80ms apart, once. With reduced motion on, they don’t animate.
    • Hover changes colour only, and only on devices with a mouse. The button is at least 44px tall.

    Files: index.html, src/App.tsx, src/Hero.tsx, src/tide.ts, src/index.css. src/tokens.css is unchanged.

    To see it, run npm run dev; I haven’t started the dev server. I can start it if you want.

    Does the hero hold? If so, the next section is the full-day current chart for SFB1204, with the tide heights at 9414290 for comparison, so it’s clear slack is not high or low tide. After that comes a short footer with the NOAA source and a second “Join the TestFlight beta” button.

15. client08

    The hero holds, with one thing missing. The card skips the flood before the 05:57 slack, 1.17 kn at 03:07, so it only shows how hard the water runs after slack and not before. Add it above the slack time, then go on to the chart.

16. genjutsu08

    Adding the 03:07 flood above the slack time, then building the chart.

    Now the chart and table styles, and adding the section to the page.

    I added the flood before slack and built the chart section; npm run build passes.

    Slack card: a row above the slack time now reads “Before it, flood, strongest: 1.17 kn at 03:07”. It’s read from the data like the rest: it’s whichever prediction comes just before the first slack.

    New section: “Slack is not high or low tide.”

    • Intro: one paragraph. A printed table gives you high and low water at the San Francisco gauge, but on 2 October 2026 each slack at SFB1204 came 10 to 50 minutes after the high or low before it at 9414290. The 10 and 50 are worked out from the data, not typed in.
    • Current chart (SFB1204, knots):
      • Flood plots above the line, ebb below.
      • The dots are NOAA’s seven predictions: slacks at 05:57, 10:31 and 16:17, and the strongest flood or ebb in between (1.17, 0.94, 1.44 and 2.11 kn).
      • The line between them draws once over 1200ms on load. Then the dots and labels fade in.
    • Tide chart (9414290, feet above MLLW): all 240 points at 6-minute steps, with high 05:47, low 09:41, high 15:58 and low 23:17 marked.
    • Slack markers: dashed lines in the accent colour run down both charts, so you can see slack landing after each high or low.
    • Caption:
      • names both stations and where they are, plus the date and the time zone;
      • says the line only joins NOAA’s points and isn’t a prediction in between;
      • says the data has nothing before 03:07 or after 19:50;
      • says the water in the cove itself isn’t measured.
    • Table: all eleven predictions from both stations in time order: time, station, what it is, and the value. The slack rows are in the accent colour and say how long after the high or low each came (“10 min after the high”). Screen readers get the table; the charts are hidden from them.

    How the chart is built: the lines are SVG stretched to the page width, and the labels are HTML on top, so the text stays readable on a phone. Below 40rem the slack labels drop the word “slack” and show only the time, so they don’t overlap. I added two tokens, --chart-stroke and --chart-dash, to MASTER.md and tokens.css.

    Files: src/DaySection.tsx (new), src/tide.ts, src/Hero.tsx, src/App.tsx, src/index.css, src/tokens.css, MASTER.md.

    The line draws on load, as the thesis says, not when you scroll to it. On a phone it will usually have finished by the time the chart comes into view.

    Does this section hold? Next is the footer: a closing “Join the TestFlight beta” button, the NOAA source link, and a short line on what the app doesn’t show. After that comes the audit.

17. client09

    It holds. Go on to the footer.

18. genjutsu09

    My replace order clobbered the variable; rewriting the file cleanly.

    The footer is built and npm run build passes.

    Closing section

    • Heading: “The beta is on TestFlight.”
    • One paragraph: Étale is in beta for iPhone through Apple’s TestFlight. There’s no Android app and no web app. It shows slack and the current between slacks, from NOAA predictions, plus an alert the evening before. It shows no water temperature.
    • A second “Join the TestFlight beta” button, linking to /beta, with exactly the same label as the one in the hero.

    Footer

    • It sits outside <main>, so screen readers treat it as the page footer.
    • The source line reads: “Figures on this page are NOAA CO-OPS predictions for 2 October 2026, fetched on 4 October 2026: current at SFB1204 and tide at 9414290. Predictions, not measurements, from stations outside the cove.”
    • The two links go to the exact NOAA requests listed in data/tide.json.
    • The bottom edge respects the iPhone safe area.

    Files: src/Closing.tsx (new), src/App.tsx, src/tide.ts, src/index.css.

    Does the footer hold? If so, I’ll run the final audit of the whole page.

19. client10

    It holds. Go ahead with the audit.

20. genjutsu10

    Loading the audit module.

    Audit script done. Now the manual checks: the thesis against the code, raw values, and contrast.

    Fixing four drifts this run introduced: the 600 weight the thesis never allowed, the raw 50% radius, the raw underline offset, and the undocumented 40rem breakpoint.

    Rerunning the tells check after the fixes, and confirming every figure on the page traces back to data/tide.json.

    The audit is done and the Étale landing page is finished; npm run build passes. I checked 11 things here and found 4 problems, all now fixed. Three checks need a browser, so they’re listed at the end for you to run.

    Problems found and fixed

    1. A third font weight. The notification title used weight 600, but the thesis says two weights. I set it to 500 and dropped 600 from the font request and from MASTER.md.
    2. Raw value: dot radius. The chart dots used a bare 50% radius; it’s now the --radius-dot token.
    3. Raw value: link underline. The underline offset was a bare 0.2em; it’s now the --underline-offset token.
    4. Breakpoints not written down. The 40rem and 52rem screen widths weren’t in MASTER.md; they are now. CSS can’t use variables there, so the values stay written out.

    The audit script still flags two things that aren’t real problems:

    • “Hover with no transition” on .btn:hover and .link:hover. The colour change is set on the base rules instead (src/index.css:447 and :484), so the hover does animate.
    • Inline heights on the two chart boxes (src/DaySection.tsx:103 and :165). These are fixed sizes that match the chart drawing, and nothing animates them.

    Checked here

    • Theses against the code:
      • entrance of 480ms with an 8px rise and 80ms between items: src/index.css:513-526;
      • the current line drawing once over 1200ms: src/index.css:531 and :550;
      • hover changes colour only, in 160ms, and only with a mouse: src/index.css:447 and :452;
      • nothing moves on scroll, and nothing loops;
      • colours, Public Sans at 400 and 500, 2px corners, no shadows: src/tokens.css.
    • Reduced motion: with it on, there’s no entrance, no line draw and no hover transition; everything appears at once (src/index.css:557).
    • Things disappearing: nothing on the page appears or disappears after load, so nothing needs an exit animation.
    • Layout properties: nothing animates width, height or position. The audit script found none.
    • Keyboard focus: the button and links show a 2px ring in the accent colour, and no focus outline is removed.
    • Five states: the button and link each have default, hover, focus, pressed and disabled.
    • Tokens: every colour and size comes from src/tokens.css.
    • Figures: all come from data/tide.json. None are typed into the page code, and there’s no temperature anywhere.
    • Contrast (body text needs 4.5:1, borders and axes need 3:1):
      • main text on the background: 12.73:1; secondary text: 6.61:1, and 5.94:1 on the card;
      • source lines on the card: 4.69:1;
      • slack colour on the background: 9.69:1;
      • button text on the pale button: 12.73:1, and 6.61:1 on the pressed grey;
      • chart axis: 3.72:1.
    • Screen readers: there are no clickable divs. The charts are hidden from screen readers, and the table under them carries the same information.
    • Patterns that can read as filler: the tells check found nothing. On a manual read, the rule on every data row and the HTML-drawn notification are both in your allowed patterns. There are no monospace labels, the page doesn’t repeat one layout section after section, and the tone stays the same throughout.

    For you to run (not checked here)

    I didn’t start a dev server or open a browser. Run npm run dev, then check:

    What to check	Pass condition
    Chrome DevTools > Performance, recorded across the page load	no frame over 16.7ms
    The page at 375, 768, 1024 and 1440px wide	no sideways scrolling, no chart labels overlapping or cut off
    The page with your system’s reduce-motion setting on	everything appears at once, with no line draw

    Things to know

    • Font: Public Sans loads from Google Fonts. No package was installed.
    • Previews: preview/thesis.html and preview/design-system.html are still there, as you asked. They were only for review, and the page doesn’t use them.
    • The -07:00 time-zone offset in src/Hero.tsx:47 is typed in rather than read from the data. It’s correct for this date (tide.json says PDT, UTC-7), but it would need changing if you used a winter date.
    • Files: MASTER.md, index.html, and in src/: tokens.css, index.css, tide.ts, App.tsx, Hero.tsx, DaySection.tsx, Closing.tsx.

    Modules loaded: tells, ui-ux-pro-max, motion-principles, css-native, mobile-principles, design-audit
    Modules not loaded: none

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