Improve scientific notation formatting

hdyc-svelte/src/lib/components/Calculator.svelte

@@ -6,6 +6,7 @@
   import QuickDefinitionCard from '$lib/components/QuickDefinitionCard.svelte';
   import QuickConversionExample from '$lib/components/QuickConversionExample.svelte';
   import QuickConversionTable from '$lib/components/QuickConversionTable.svelte';
+  import ScientificNotationValue from '$lib/components/ScientificNotationValue.svelte';
 
   export let config: CalculatorDef;
   export let showTitle = true;
@@ -147,7 +148,9 @@
     </button>
     {#if config.factor && config.type === 'standard'}
       <span class="formula-hint">
-        1 {config.labels.in1} = {config.factor}{config.offset ? ` + ${config.offset}` : ''} {config.labels.in2}
+        1 {config.labels.in1} =
+        <ScientificNotationValue value={config.factor} />
+        {config.offset ? ` + ${config.offset}` : ''} {config.labels.in2}
       </span>
     {/if}
   </div>

hdyc-svelte/src/lib/components/QuickConversionExample.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
   import { solve } from '$lib/engine';
   import type { CalculatorDef } from '$lib/data/calculators';
+  import ScientificNotationValue from '$lib/components/ScientificNotationValue.svelte';
 
   export let config: CalculatorDef;
 
@@ -17,10 +18,6 @@
     ? solve(config, 1, exampleInput.toString(), '', '')
     : null;
   $: offset = config.offset ?? 0;
-  $: formulaExpression = supportsExample
-    ? `${exampleInput} × ${config.factor}${offset ? ` + ${offset}` : ''}`
-    : '';
-
   const formatExampleValue = (value: number | null): string => {
     if (value === null || Number.isNaN(value)) {
       return '—';
@@ -50,17 +47,27 @@
   <section class="example-card">
     <h3>How to convert {config.labels.in1} to {config.labels.in2}</h3>
     <p class="example-note">
-      1 {config.labels.in1} = {config.factor}{config.offset ? ` + ${config.offset}` : ''} {config.labels.in2}
+      1 {config.labels.in1} =
+      <ScientificNotationValue value={config.factor} />
+      {config.offset ? ` + ${config.offset}` : ''} {config.labels.in2}
     </p>
     <p class="example-note">
-      1 {config.labels.in2} = {formattedReverseValue} {config.labels.in1}
+      1 {config.labels.in2} =
+      <ScientificNotationValue value={formattedReverseValue} fallback="—" />
+      {config.labels.in1}
     </p>
     <p class="example-line">
       Example: convert {exampleInput} {config.labels.in1} to {config.labels.in2}
     </p>
     <p class="example-line">
-      {formulaExpression} =
-      <span class="example-result">{result.val2} {config.labels.in2}</span>
+      {exampleInput}
+      <span class="example-operator">×</span>
+      <ScientificNotationValue value={config.factor} />
+      {config.offset ? ` + ${config.offset}` : ''}
+      =
+      <span class="example-result">
+        <ScientificNotationValue value={result.val2} fallback="—" /> {config.labels.in2}
+      </span>
     </p>
   </section>
 {/if}
@@ -93,6 +100,11 @@
     color: var(--text);
   }
 
+  .example-operator {
+    margin: 0 0.25rem;
+    font-weight: 600;
+  }
+
   .example-result {
     font-weight: 600;
     margin-left: 0.35rem;

hdyc-svelte/src/lib/components/QuickConversionTable.svelte

@@ -1,20 +1,19 @@
 <script lang="ts">
   import { solve } from '$lib/engine';
-  import { parseScientificNotation, type ScientificNotationParts } from '$lib/utils/formatScientific';
+  import ScientificNotationValue from '$lib/components/ScientificNotationValue.svelte';
   import type { CalculatorDef } from '$lib/data/calculators';
 
   export let config: CalculatorDef;
 
   const numericSamples = [0.1, 0.5, 1, 2, 5, 10, 20, 50, 100];
 
-  type Row = { input: number; output: string; scientific?: ScientificNotationParts };
+  type Row = { input: number; output: string };
 
   const buildRow = (value: number): Row => {
     const formatted = solve(config, 1, value.toString(), '', '');
     return {
       input: value,
       output: formatted.val2 || '—',
-      scientific: formatted.val2 ? parseScientificNotation(formatted.val2) ?? undefined : undefined,
     };
   };
 
@@ -45,14 +44,7 @@
           <p class="chart-statement">
             Converting {row.input} <span class="chart-unit">{inputLabel}</span> into <span class="chart-unit">{outputLabel}</span> equals
             <span class="chart-output-value">
-              {#if row.scientific}
-                <span class="scientific-base">{row.scientific.base}</span>
-                <span class="scientific-suffix">
-                  ×10<sup>{row.scientific.exponent}</sup>
-                </span>
-              {:else}
-                {row.output}
-              {/if}
+              <ScientificNotationValue value={row.output} fallback="—" />
             </span>
             <span class="chart-output-unit">{outputLabel}</span>.
           </p>

hdyc-svelte/src/lib/components/ScientificNotationValue.svelte

@@ -0,0 +1,46 @@
+<script lang="ts">
+  import { parseScientificNotation, type ScientificNotationParts } from '$lib/utils/formatScientific';
+
+  export let value: string | number | null | undefined = null;
+  export let fallback = '—';
+  export let className = '';
+
+  const formattedValue = value == null ? '' : `${value}`;
+  const scientific: ScientificNotationParts | null = formattedValue
+    ? parseScientificNotation(formattedValue)
+    : null;
+</script>
+
+{#if scientific}
+  <span class={`scientific-notation ${className}`.trim()}>
+    <span class="scientific-base">{scientific.base}</span>
+    <span class="scientific-suffix">
+      ×10<sup>{scientific.exponent}</sup>
+    </span>
+  </span>
+{:else}
+  <span class={`scientific-plain ${className}`.trim()}>
+    {formattedValue || fallback}
+  </span>
+{/if}
+
+<style>
+  .scientific-notation,
+  .scientific-plain {
+    display: inline-flex;
+    align-items: baseline;
+    gap: 0.15rem;
+  }
+
+  .scientific-suffix {
+    display: inline-flex;
+    align-items: baseline;
+    gap: 0.15rem;
+    font-size: 0.85em;
+  }
+
+  .scientific-suffix sup {
+    font-size: 0.75em;
+    vertical-align: super;
+  }
+</style>

hdyc-svelte/src/routes/[slug]/+page.svelte

@@ -5,6 +5,7 @@
   import { onMount } from 'svelte';
   import type { PageData } from './$types';
   import { buildSeoMeta, canonicalUrl, SITE_NAME, SITE_URL, toJsonLd } from '$lib/seo';
+  import ScientificNotationValue from '$lib/components/ScientificNotationValue.svelte';
 
   export let data: PageData;
 
@@ -105,14 +106,18 @@
       <p>
         The conversion between {calc.labels.in1.toLowerCase()} and {calc.labels.in2.toLowerCase()}
         uses a fixed multiplication factor. One {calc.labels.in1.toLowerCase().replace(/s$/, '')} equals
-        {calc.factor}{calc.offset ? ` plus an offset of ${calc.offset}` : ''} {calc.labels.in2.toLowerCase()}.
+        <ScientificNotationValue value={calc.factor} />
+        {calc.offset ? ` plus an offset of ${calc.offset}` : ''} {calc.labels.in2.toLowerCase()}.
         {#if calc.offset}
           This offset is common in temperature conversions, where scales differ not just in magnitude but also in their zero point.
         {/if}
       </p>
       <p>
-        To convert, multiply the value in {calc.labels.in1.toLowerCase()} by {calc.factor}{calc.offset ? `, then add ${calc.offset}` : ''}.
-        To convert in the opposite direction, {calc.offset ? `subtract ${calc.offset}, then ` : ''}divide by {calc.factor}.
+        To convert, multiply the value in {calc.labels.in1.toLowerCase()} by
+        <ScientificNotationValue value={calc.factor} />
+        {calc.offset ? `, then add ${calc.offset}` : ''}.
+        To convert in the opposite direction, {calc.offset ? `subtract ${calc.offset}, then ` : ''}divide by
+        <ScientificNotationValue value={calc.factor} />.
       </p>
     {:else if calc.type === '3col' || calc.type === '3col-mul'}
       <p>