Phase 1: scaffold, types, schema, layout shell

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/assets/favicon.svg

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+<svg xmlns="http://www.w3.org/2000/svg" width="107" height="128" viewBox="0 0 107 128"><title>svelte-logo</title><path d="M94.157 22.819c-10.4-14.885-30.94-19.297-45.792-9.835L22.282 29.608A29.92 29.92 0 0 0 8.764 49.65a31.5 31.5 0 0 0 3.108 20.231 30 30 0 0 0-4.477 11.183 31.9 31.9 0 0 0 5.448 24.116c10.402 14.887 30.942 19.297 45.791 9.835l26.083-16.624A29.92 29.92 0 0 0 98.235 78.35a31.53 31.53 0 0 0-3.105-20.232 30 30 0 0 0 4.474-11.182 31.88 31.88 0 0 0-5.447-24.116" style="fill:#ff3e00"/><path d="M45.817 106.582a20.72 20.72 0 0 1-22.237-8.243 19.17 19.17 0 0 1-3.277-14.503 18 18 0 0 1 .624-2.435l.49-1.498 1.337.981a33.6 33.6 0 0 0 10.203 5.098l.97.294-.09.968a5.85 5.85 0 0 0 1.052 3.878 6.24 6.24 0 0 0 6.695 2.485 5.8 5.8 0 0 0 1.603-.704L69.27 76.28a5.43 5.43 0 0 0 2.45-3.631 5.8 5.8 0 0 0-.987-4.371 6.24 6.24 0 0 0-6.698-2.487 5.7 5.7 0 0 0-1.6.704l-9.953 6.345a19 19 0 0 1-5.296 2.326 20.72 20.72 0 0 1-22.237-8.243 19.17 19.17 0 0 1-3.277-14.502 17.99 17.99 0 0 1 8.13-12.052l26.081-16.623a19 19 0 0 1 5.3-2.329 20.72 20.72 0 0 1 22.237 8.243 19.17 19.17 0 0 1 3.277 14.503 18 18 0 0 1-.624 2.435l-.49 1.498-1.337-.98a33.6 33.6 0 0 0-10.203-5.1l-.97-.294.09-.968a5.86 5.86 0 0 0-1.052-3.878 6.24 6.24 0 0 0-6.696-2.485 5.8 5.8 0 0 0-1.602.704L37.73 51.72a5.42 5.42 0 0 0-2.449 3.63 5.79 5.79 0 0 0 .986 4.372 6.24 6.24 0 0 0 6.698 2.486 5.8 5.8 0 0 0 1.602-.704l9.952-6.342a19 19 0 0 1 5.295-2.328 20.72 20.72 0 0 1 22.237 8.242 19.17 19.17 0 0 1 3.277 14.503 18 18 0 0 1-8.13 12.053l-26.081 16.622a19 19 0 0 1-5.3 2.328" style="fill:#fff"/></svg>

src/lib/config.ts

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+/**
+ * Number display configuration.
+ * Adjust these constants to change how conversion results are formatted.
+ */
+
+/** If set, zero-pads the integer part to this many digits. Unset = show as-is. */
+export const INTEGER_DIGITS: number | undefined = undefined;
+
+/** Number of decimal places to show (fixed-point). */
+export const FRACTIONAL_DIGITS: number = 8;
+
+/**
+ * Output grid layout configuration.
+ * Grid uses CSS Grid repeat(auto-fill, minmax(MIN_COLUMN_WIDTH, 1fr)).
+ * Column count is automatic — determined by available width ÷ (MIN_COLUMN_WIDTH + GRID_GAP).
+ */
+
+/** Minimum tile width for the output grid. Controls automatic column count. */
+export const MIN_COLUMN_WIDTH: string = '160px';
+
+/** Gap between output grid tiles. Used for both row and column gaps. */
+export const GRID_GAP: string = '1rem';

src/lib/convert.ts

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+import { Big } from 'big.js';
+import type { Unit } from './types';
+
+/**
+ * Convert a value from one unit to another using canonical base-unit factors.
+ * Uses big.js for all arithmetic to avoid floating-point precision loss.
+ * Pure function — no side effects, no imports of the unit registry.
+ */
+export function convert(value: Big, from: Unit, to: Unit): Big {
+  if (from.id === to.id) return value;
+  const inBase = value.times(from.toBase);
+  return inBase.div(to.toBase);
+}
+
+/**
+ * Convert a value using unit IDs, looking up from a provided registry.
+ * Accepts a number or Big for the input value.
+ * Throws if either ID is not found.
+ */
+export function convertById(
+  value: number | Big,
+  fromId: string,
+  toId: string,
+  units: Unit[]
+): Big {
+  const from = units.find((u) => u.id === fromId);
+  const to = units.find((u) => u.id === toId);
+  if (!from) throw new Error(`Unknown unit id: ${fromId}`);
+  if (!to) throw new Error(`Unknown unit id: ${toId}`);
+  return convert(Big(value), from, to);
+}

src/lib/index.ts

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+// place files you want to import through the `$lib` alias in this folder.

src/lib/types.ts

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+/**
+ * A single unit in the custom unit system.
+ * All conversion passes through the canonical base unit (toBase factor).
+ */
+export interface Unit {
+  /** Machine identifier. Stable, kebab-case. Never shown to user. */
+  id: string;
+
+  /** Human-readable singular display name. Shown in UI labels. */
+  label: string;
+
+  /** Human-readable plural display name. Used in result rows ("12 blurbs"). */
+  labelPlural: string;
+
+  /** Short symbol or abbreviation for compact display. */
+  symbol: string;
+
+  /**
+   * Conversion factor to canonical base unit for this group.
+   * The base unit itself has toBase = 1.0.
+   * To convert A → B: result = valueA * A.toBase / B.toBase
+   */
+  toBase: number;
+
+  /** Optional grouping tag for multi-group converters. */
+  group?: string;
+}
+
+/** A named collection of units sharing a base unit. */
+export interface UnitGroup {
+  id: string;
+  label: string;
+  units: Unit[];
+}

src/lib/units/definitions.ts

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+import type { Unit } from '../types';
+
+/**
+ * Invented unit group: Florp measurement system.
+ * Base unit: "blurb" (toBase = 1.0). All others defined relative to it.
+ */
+export const florpUnits: Unit[] = [
+  {
+    id: 'blurb',
+    label: 'Blurb',
+    labelPlural: 'Blurbs',
+    symbol: 'bl',
+    toBase: 1.0,
+    group: 'florp',
+  },
+  {
+    id: 'snorp',
+    label: 'Snorp',
+    labelPlural: 'Snorps',
+    symbol: 'sn',
+    toBase: 7.5,
+    group: 'florp',
+  },
+  {
+    id: 'krumble',
+    label: 'Krumble',
+    labelPlural: 'Krumbles',
+    symbol: 'kr',
+    toBase: 0.25,
+    group: 'florp',
+  },
+  {
+    id: 'wobbit',
+    label: 'Wobbit',
+    labelPlural: 'Wobbits',
+    symbol: 'wb',
+    toBase: 144.0,
+    group: 'florp',
+  },
+];