feat: two-line cards, responsive grid, real uniform font size

BACKLOG.md

@@ -15,13 +15,6 @@ In dark mode the "Clear" button text lightens on hover, giving visual feedback.
 mode and Dan mode it currently does nothing visible. Should have a matching subtle
 highlight (e.g. text darkens, underline appears, or border darkens).
 
-### Admin: user-provided IDs for units and groups
-When creating a unit or group, allow the user to optionally supply their own ID.
-- If the ID field is left empty, auto-generate it by kebab-casing the label (live
-  preview as the user types the label).
-- If the user types into the ID field, stop auto-generating and use what they typed.
-- Validate: IDs must be unique and slug-safe.
-
 ### Admin: allow renaming unit and group IDs
 The edit forms do not currently expose the `id` field for existing units or groups.
 
@@ -46,11 +39,6 @@ Per-group setting controlling whether units are displayed on the front end in:
 Data shape change: add optional `sortOrder?: 'defined' | 'alpha'` to the `Group` type
 (default: `'defined'`).
 
-### Admin: drag-to-reorder units within a group
-Allow units to be reordered within their group via drag-and-drop in the left panel.
-Order is persisted to `units.json`. Only meaningful when the group's `sortOrder` is
-`'defined'`.
-
 ### Admin: unsaved-form guard on "Add Unit" / "Add Group"
 If the user is in the middle of filling out a create/edit form and clicks "+ Add Unit"
 or "+ Add Group", the current form should be auto-saved before opening the new one.

src/app.css

@@ -2,8 +2,8 @@
 
 /* CSS custom properties (set dynamically via inline style from ConverterCard) */
 :root {
-  --min-col-width: 160px;
   --grid-gap: 1rem;
+  --card-font-size: 1rem; /* overridden per-grid by uniformFontSize action */
 
   /* Shadow for card elevation (theme-neutral) */
   --shadow-color: 30deg 8% 20%;
@@ -238,13 +238,28 @@
 }
 
 /* ── Results grid ──────────────────────────────────────────────────────────── */
+/* Responsive column count: 1 col mobile, 2 col tablet, 3 col desktop.        */
+/* Cards grow to fill available space (1fr). Column count is a minimum —      */
+/* more columns are fine if content allows.                                    */
 .results-grid {
   display: grid;
-  grid-template-columns: repeat(auto-fit, minmax(var(--min-col-width), 1fr));
+  grid-template-columns: 1fr;
   gap: var(--grid-gap);
   margin-top: 1.5rem;
 }
 
+@media (min-width: 480px) {
+  .results-grid {
+    grid-template-columns: repeat(2, 1fr);
+  }
+}
+
+@media (min-width: 900px) {
+  .results-grid {
+    grid-template-columns: repeat(3, 1fr);
+  }
+}
+
 /* ── Result tile ───────────────────────────────────────────────────────────── */
 .result-tile {
   cursor: pointer;
@@ -256,6 +271,9 @@
   display: flex;
   flex-direction: column;
   gap: 0.2rem;
+  /* Fixed two-line height so all cards are the same size */
+  min-height: 4.5rem;
+  justify-content: center;
   transition: background-color 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
   user-select: none;
   /* Pico's [role=button] rule sets --pico-color: var(--pico-primary-inverse)
@@ -272,16 +290,21 @@
 }
 
 .result-value {
-  font-size: 1rem;
+  font-size: var(--card-font-size, 1rem);
   font-weight: 600;
   font-variant-numeric: tabular-nums;
-  word-break: break-all;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
   /* color inherits from .result-tile which has already corrected for Pico's button reset */
 }
 
 .result-label {
-  font-size: 0.85rem;
+  font-size: var(--card-font-size, 0.85rem);
   color: var(--color-label);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
 }
 
 /* .result-symbol removed — symbol is now rendered inline in the label */

src/components/ConversionResult.svelte

@@ -6,6 +6,10 @@
 
   /**
    * ConversionResult — displays one conversion result tile.
+   * Always two-line layout:
+   *   Line 1: converted value (large, prominent)
+   *   Line 2: unit label + symbol (smaller/muted)
+   *
    * Emits onclick (highlight), onshiftclick (make input unit),
    * and onctrlclick (adopt value) events.
    * Handles nullable value for cross-group N/A state.
@@ -59,13 +63,15 @@
   aria-label={value !== null ? `${formattedValue} ${unit.labelPlural}` : `N/A ${unit.labelPlural}`}
   aria-pressed={highlighted}
 >
-  {#if value === null}
-    <span class="result-value result-na">N/A</span>
-  {:else}
-    <span class="result-value">
+  <!-- Line 1: the converted value -->
+  <span class="result-value" class:result-na={value === null}>
+    {#if value !== null}
       {#if isYolo}<span class="yolo-tilde">~</span>{/if}{formattedValue}
-    </span>
+    {:else}
+      N/A
     {/if}
+  </span>
+  <!-- Line 2: label + symbol -->
   <span class="result-label" use:tooltip={unit.description ?? ''}>{unit.labelPlural} ({unit.symbol})</span>
 </div>
 

src/components/ConverterCard.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import type { Unit, Group, ResultItem } from '$lib/types';
   import type { Big } from 'big.js';
-  import { MIN_COLUMN_WIDTH, GRID_GAP } from '$lib/config';
+  import { uniformFontSize } from '$lib/actions/uniformFontSize';
   import UnitInput from './UnitInput.svelte';
   import UnitDropdown from './UnitDropdown.svelte';
   import ConversionResult from './ConversionResult.svelte';
@@ -33,8 +33,6 @@
     onsetinput: (id: string) => void;
     onctrlclick: (id: string, value: Big) => void;
   } = $props();
-
-  const gridStyle = `--min-col-width: ${MIN_COLUMN_WIDTH}; --grid-gap: ${GRID_GAP};`;
 </script>
 
 <article>
@@ -47,7 +45,7 @@
     {#if orderedResults.length > 1 && section.groupLabel}
       <div class="group-divider">{section.groupLabel}</div>
     {/if}
-    <div class="results-grid" style={gridStyle}>
+    <div class="results-grid" use:uniformFontSize={{ results: section.items }}>
       {#each section.items as item (item.unit.id)}
         <ConversionResult
           value={item.convertedValue}

src/lib/actions/uniformFontSize.ts

@@ -0,0 +1,181 @@
+/**
+ * uniformFontSize — Svelte action that computes and applies a single font size
+ * to all cards in a results grid so the widest content still fits.
+ *
+ * Usage:
+ *   <div class="results-grid" use:uniformFontSize={{ results }}>
+ *
+ * How it works:
+ *   1. After each render (via tick()), for every .result-tile in the container:
+ *      - Measure available inner width (clientWidth − horizontal padding)
+ *      - Measure rendered text width of .result-value and .result-label using
+ *        an off-screen span with matching font properties
+ *      - Compute scale = availableWidth / max(valueWidth, labelWidth)
+ *   2. Take minimum scale across all tiles (tightest tile wins)
+ *   3. Clamp: min 0.6rem (floor), max = base font size (never inflate)
+ *   4. Set --card-font-size on the container
+ *   5. For any element still overflowing at the floor, add ellipsis + title
+ *
+ * ResizeObserver on the container re-runs measurement, debounced 50 ms.
+ */
+
+import { tick } from 'svelte';
+import { browser } from '$app/environment';
+
+export interface UniformFontSizeParams {
+  /** Pass the current results array; any change triggers re-measurement. */
+  results: unknown;
+}
+
+// Base font size we scale from (1rem). Expressed in px at measure time.
+const BASE_REM = 1; // rem
+const FLOOR_REM = 0.6; // rem
+const DEBOUNCE_MS = 50;
+
+/** Return the computed horizontal padding (left + right) of an element in px. */
+function horizontalPadding(el: HTMLElement): number {
+  const style = window.getComputedStyle(el);
+  return parseFloat(style.paddingLeft) + parseFloat(style.paddingRight);
+}
+
+/** Measure the rendered pixel width of `text` at `fontSize`px using a hidden span. */
+function measureText(
+  text: string,
+  fontSize: number,
+  fontWeight: string,
+  fontFamily: string,
+  span: HTMLSpanElement
+): number {
+  span.style.fontSize = `${fontSize}px`;
+  span.style.fontWeight = fontWeight;
+  span.style.fontFamily = fontFamily;
+  span.textContent = text;
+  return span.getBoundingClientRect().width;
+}
+
+/** Get root font size in px (for rem→px conversion). */
+function getRootFontSizePx(): number {
+  return parseFloat(getComputedStyle(document.documentElement).fontSize) || 16;
+}
+
+export function uniformFontSize(
+  node: HTMLElement,
+  params: UniformFontSizeParams
+): { update: (p: UniformFontSizeParams) => void; destroy: () => void } {
+  if (!browser) {
+    return { update: () => {}, destroy: () => {} };
+  }
+
+  // Off-screen measurement span — created once, reused, destroyed on action teardown.
+  const measureSpan = document.createElement('span');
+  measureSpan.style.cssText =
+    'position:fixed;top:-9999px;left:-9999px;visibility:hidden;white-space:nowrap;pointer-events:none;';
+  document.body.appendChild(measureSpan);
+
+  let debounceTimer: ReturnType<typeof setTimeout> | null = null;
+  let observer: ResizeObserver | null = null;
+
+  async function measure() {
+    // Wait for Svelte to flush DOM updates.
+    await tick();
+
+    const tiles = Array.from(node.querySelectorAll<HTMLElement>('.result-tile'));
+    if (tiles.length === 0) return;
+
+    const rootPx = getRootFontSizePx();
+    const basePx = BASE_REM * rootPx;
+    const floorPx = FLOOR_REM * rootPx;
+
+    let minScale = 1; // never inflate above base
+
+    for (const tile of tiles) {
+      const availableWidth = tile.clientWidth - horizontalPadding(tile);
+      if (availableWidth <= 0) continue;
+
+      const valueEl = tile.querySelector<HTMLElement>('.result-value');
+      const labelEl = tile.querySelector<HTMLElement>('.result-label');
+      if (!valueEl || !labelEl) continue;
+
+      // Get font properties from the live elements (inherits CSS vars etc.)
+      const valueStyle = window.getComputedStyle(valueEl);
+      const labelStyle = window.getComputedStyle(labelEl);
+
+      const valueText = valueEl.textContent ?? '';
+      const labelText = labelEl.textContent ?? '';
+
+      const valueWidth = measureText(
+        valueText,
+        basePx,
+        valueStyle.fontWeight,
+        valueStyle.fontFamily,
+        measureSpan
+      );
+      const labelWidth = measureText(
+        labelText,
+        basePx,
+        labelStyle.fontWeight,
+        labelStyle.fontFamily,
+        measureSpan
+      );
+
+      const maxTextWidth = Math.max(valueWidth, labelWidth);
+      if (maxTextWidth <= 0) continue;
+
+      const scale = availableWidth / maxTextWidth;
+      if (scale < minScale) minScale = scale;
+    }
+
+    // Compute final font size in rem, clamped to floor.
+    const computedPx = Math.max(floorPx, basePx * minScale);
+    const computedRem = computedPx / rootPx;
+
+    node.style.setProperty('--card-font-size', `${computedRem.toFixed(4)}rem`);
+
+    // Apply truncation on elements that still overflow at the floor.
+    if (computedPx <= floorPx + 0.01) {
+      for (const tile of tiles) {
+        for (const selector of ['.result-value', '.result-label']) {
+          const el = tile.querySelector<HTMLElement>(selector);
+          if (!el) continue;
+          if (el.scrollWidth > el.clientWidth) {
+            el.style.overflow = 'hidden';
+            el.style.whiteSpace = 'nowrap';
+            el.style.textOverflow = 'ellipsis';
+            el.title = el.textContent ?? '';
+          }
+        }
+      }
+    }
+  }
+
+  function scheduleMeasure() {
+    if (debounceTimer !== null) clearTimeout(debounceTimer);
+    debounceTimer = setTimeout(() => {
+      debounceTimer = null;
+      measure();
+    }, DEBOUNCE_MS);
+  }
+
+  // Initial measurement (after first render).
+  measure();
+
+  // ResizeObserver — single observer on the grid container.
+  observer = new ResizeObserver(scheduleMeasure);
+  observer.observe(node);
+
+  return {
+    update(_newParams: UniformFontSizeParams) {
+      // Called by Svelte whenever the `results` prop changes — re-measure.
+      measure();
+    },
+    destroy() {
+      observer?.disconnect();
+      observer = null;
+      if (debounceTimer !== null) {
+        clearTimeout(debounceTimer);
+        debounceTimer = null;
+      }
+      measureSpan.remove();
+    }
+  };
+}