/* ==========================================================================
   1. Tokens
   ========================================================================== */
:root {
  --bg: #f2f6fb;
  --surface: #ffffff;
  --ink: #13232f;
  --ink-soft: #57697a;
  --border: #dde6ef;
  --accent: #1f6fb8;
  --accent-dark: #145089;
  --accent-ink: #ffffff;
  --accent-soft: #e7f1fb;
  --cta: #ef8a1f;
  --cta-dark: #d3760f;
  --cta-ink: #1a1408;
  --danger: #c4402f;
  --radius: 18px;
  --radius-sm: 11px;
  --sans: "Inter", system-ui, sans-serif;
  --display: "Manrope", var(--sans);
  --mono: "JetBrains Mono", ui-monospace, monospace;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --shadow-sm: 0 1px 2px rgba(19, 35, 47, .06);
  --shadow-md: 0 10px 28px rgba(19, 35, 47, .12);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c1620;
    --surface: #121e29;
    --ink: #eef4f9;
    --ink-soft: #a8b9c7;
    --border: #253647;
    --accent: #5aa5e6;
    --accent-dark: #3d84c4;
    --accent-ink: #06131e;
    --accent-soft: #142b3d;
    --cta: #f5a23e;
    --cta-dark: #e08a20;
    --cta-ink: #1a1408;
  }
}

/* ==========================================================================
   2. Reset
   ========================================================================== */
*, *::before, *::after { box-sizing: border-box; margin: 0; }
html { -webkit-text-size-adjust: 100%; tab-size: 2; }
body {
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: clip;
}
img, svg, video { display: block; max-width: 100%; }
button { font: inherit; color: inherit; cursor: pointer; border: 0; background: none; }
a { color: inherit; text-decoration: none; }
input, select { font: inherit; color: inherit; }
p { text-wrap: pretty; }
h1, h2, h3 { font-family: var(--display); text-wrap: balance; line-height: 1.15; letter-spacing: -0.01em; color: var(--ink); }
::selection { background: var(--accent); color: var(--accent-ink); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 6px; }

.skip-link {
  position: fixed; top: -100px; left: 1rem;
  padding: .6rem 1rem; background: var(--ink); color: var(--bg);
  z-index: 9999; border-radius: 8px; font-weight: 600;
}
.skip-link:focus { top: 1rem; }

.wrap { max-width: 960px; margin-inline: auto; padding-inline: 1.25rem; }

/* ==========================================================================
   3. Header / Footer
   ========================================================================== */
.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--surface);
  position: sticky; top: 0; z-index: 20;
  box-shadow: 0 1px 0 rgba(19, 35, 47, .03);
}
.site-header__inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { display: flex; align-items: center; gap: .55rem; height: 100%; }
.brand__logo { height: 34px; width: 34px; display: block; flex-shrink: 0; }
.brand__text {
  font-family: var(--display); font-weight: 800; font-size: .95rem;
  letter-spacing: .02em; color: var(--ink); white-space: nowrap;
}
.brand__sub { font-weight: 500; color: var(--ink-soft); font-size: .85em; }
.site-header__nav { display: none; gap: 1rem; align-items: center; font-size: .92rem; font-weight: 600; }
.site-header__nav a:not(.nav-cta):hover { color: var(--accent); }
.nav-cta {
  display: inline-flex; align-items: center;
  padding: .5rem 1rem;
  background: var(--accent);
  color: var(--accent-ink);
  border-radius: 999px;
  font-weight: 700;
  transition: background .15s var(--ease-out), transform .15s var(--ease-out);
}
.nav-cta:hover { background: var(--accent-dark); transform: translateY(-1px); }
@media (min-width: 720px) { .site-header__nav { display: flex; } }

.site-footer { border-top: 1px solid var(--border); margin-top: 3rem; padding-block: 2rem; color: var(--ink-soft); font-size: .9rem; }
.site-footer__inner { display: flex; flex-direction: column; gap: 1rem; align-items: center; text-align: center; }
.site-footer__inner nav { display: flex; gap: 1.25rem; flex-wrap: wrap; justify-content: center; }
.site-footer__inner nav a:hover { color: var(--accent); }
@media (min-width: 720px) { .site-footer__inner { flex-direction: row; justify-content: space-between; text-align: left; } }

/* ==========================================================================
   4. Hero
   ========================================================================== */
.hero {
  padding-block: 2.75rem 1.5rem;
  text-align: center;
  background: radial-gradient(120% 140% at 50% -10%, var(--accent-soft) 0%, transparent 60%);
}
.hero h1 { font-size: clamp(1.6rem, 4.5vw, 2.4rem); }
.hero__subtitle { margin-top: .75rem; color: var(--ink-soft); font-size: 1.05rem; max-width: 620px; margin-inline: auto; }

/* ==========================================================================
   5. Tool card
   ========================================================================== */
.tool-section { padding-bottom: .5rem; }

.tool-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  padding: 1.25rem;
}

.tool-card__categories {
  display: flex; flex-wrap: wrap; gap: .5rem;
  margin-bottom: 1.1rem;
}
.category-btn {
  display: inline-flex; align-items: center; gap: .4rem;
  padding: .5rem .85rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: .88rem; font-weight: 600;
  color: var(--ink-soft);
  background: var(--bg);
  transition: background .15s var(--ease-out), color .15s var(--ease-out), border-color .15s var(--ease-out);
  white-space: nowrap;
}
.category-btn svg { width: 16px; height: 16px; }
.category-btn:hover { border-color: var(--accent); color: var(--ink); }
.category-btn[aria-selected="true"] {
  background: var(--accent); border-color: var(--accent); color: var(--accent-ink);
}

input, select { min-width: 0; max-width: 100%; }

.field-group {
  display: grid;
  grid-template-columns: 1fr;
  gap: .85rem;
  align-items: end;
  min-width: 0;
}
@media (min-width: 640px) {
  .field-group { grid-template-columns: minmax(0,1fr) minmax(0,1fr) auto minmax(0,1fr); }
}

.field { display: flex; flex-direction: column; gap: .35rem; min-width: 0; }
.field__label { font-size: .8rem; font-weight: 700; color: var(--ink-soft); text-transform: uppercase; letter-spacing: .03em; }
.field input, .field select {
  width: 100%;
  padding: .75rem .85rem;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  font-size: 1.05rem;
  font-weight: 600;
  transition: border-color .15s var(--ease-out);
}
.field input:focus, .field select:focus { border-color: var(--accent); }
.field input { font-family: var(--mono); }

.swap-btn {
  align-self: center;
  width: 42px; height: 42px;
  display: grid; place-items: center;
  border: 1.5px solid var(--border);
  border-radius: 50%;
  background: var(--surface);
  transition: background .15s var(--ease-out), transform .2s var(--ease-out);
  justify-self: center;
}
.swap-btn svg { width: 20px; height: 20px; color: var(--accent); }
.swap-btn:hover { background: var(--accent-soft); }
.swap-btn:active { transform: rotate(180deg); }
@media (prefers-reduced-motion: reduce) { .swap-btn:active { transform: none; } }

.convert-error {
  margin-top: .6rem;
  color: var(--danger);
  font-size: .88rem;
  font-weight: 600;
}

.result-box {
  margin-top: 1.1rem;
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  flex-wrap: wrap;
  background: var(--accent-soft);
  border: 1px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 1rem 1.1rem;
}
.result-box__value {
  font-family: var(--mono);
  font-size: clamp(1.3rem, 4vw, 1.7rem);
  font-weight: 700;
  color: var(--ink);
  word-break: break-word;
}
.copy-btn {
  display: inline-flex; align-items: center; gap: .4rem;
  padding: .55rem .8rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .85rem; font-weight: 700;
  transition: border-color .15s var(--ease-out);
}
.copy-btn svg { width: 16px; height: 16px; }
.copy-btn:hover { border-color: var(--accent); }

.download-btn {
  margin-top: .9rem;
  width: 100%;
  padding: .8rem 1rem;
  border: 1.5px dashed var(--cta);
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-size: .92rem;
  color: var(--cta-dark);
  background: color-mix(in srgb, var(--cta) 8%, transparent);
  transition: border-color .15s var(--ease-out), background .15s var(--ease-out);
}
.download-btn:hover { border-style: solid; background: color-mix(in srgb, var(--cta) 16%, transparent); }

.privacy-badge {
  margin-top: 1rem;
  font-size: .82rem;
  color: var(--ink-soft);
  text-align: center;
}

/* ==========================================================================
   6. Ad slots (placeholders)
   ========================================================================== */
.ad-slot {
  border: 1.5px dashed var(--border);
  border-radius: var(--radius-sm);
  display: grid; place-items: center;
  color: var(--ink-soft);
  font-size: .8rem;
  font-weight: 700;
  letter-spacing: .08em;
  background: repeating-linear-gradient(45deg, transparent, transparent 10px, rgba(0,0,0,.02) 10px, rgba(0,0,0,.02) 20px);
}
.ad-slot__label { opacity: .6; }
.ad-slot--leaderboard { min-height: 90px; margin-block: 1.5rem; }
.ad-slot--incontent { min-height: 250px; margin-block: 1.5rem; max-width: 336px; margin-inline: auto; }
.ad-slot--popup { min-height: 200px; width: 100%; }
.ad-slot--corner { min-height: 100px; width: 100%; }

/* ==========================================================================
   7. Steps
   ========================================================================== */
.steps { padding-block: 2.5rem; }
.steps h2 { text-align: center; font-size: clamp(1.3rem, 3vw, 1.7rem); margin-bottom: 1.75rem; }
.steps__list { list-style: none; display: grid; gap: 1.25rem; }
@media (min-width: 720px) { .steps__list { grid-template-columns: repeat(3, minmax(0,1fr)); } }
.steps__list li {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
}
.steps__list svg { width: 28px; height: 28px; color: var(--accent); margin-bottom: .75rem; }
.steps__list h3 { font-size: 1.05rem; margin-bottom: .4rem; }
.steps__list p { color: var(--ink-soft); font-size: .92rem; }

/* ==========================================================================
   8. SEO text
   ========================================================================== */
.seo-text { padding-block: 1rem 2rem; }
.seo-text h2 { font-size: clamp(1.25rem, 3vw, 1.55rem); margin-bottom: 1rem; }
.seo-text p { color: var(--ink-soft); margin-bottom: 1rem; max-width: 72ch; }
.seo-text p:last-child { margin-bottom: 0; }

/* ==========================================================================
   9. Related instruments
   ========================================================================== */
.related { padding-block: 1rem 2.5rem; }
.related h2 { font-size: clamp(1.25rem, 3vw, 1.55rem); }
.related__intro { color: var(--ink-soft); margin-block: .6rem 1.25rem; max-width: 65ch; }
.related__grid { display: grid; gap: 1rem; grid-template-columns: repeat(2, 1fr); }
@media (min-width: 720px) { .related__grid { grid-template-columns: repeat(3, minmax(0,1fr)); } }
.related__card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem;
  transition: border-color .15s var(--ease-out), transform .15s var(--ease-out);
}
.related__card:hover { border-color: var(--accent); transform: translateY(-2px); }
.related__card__tag { display: inline-block; font-size: .72rem; font-weight: 700; color: var(--accent); text-transform: uppercase; letter-spacing: .04em; margin-bottom: .4rem; }
.related__card h3 { font-size: .95rem; }

/* ==========================================================================
   10. FAQ
   ========================================================================== */
.faq { padding-block: 1rem 2.5rem; }
.faq h2 { font-size: clamp(1.25rem, 3vw, 1.55rem); margin-bottom: 1.25rem; }
.faq-item {
  border-bottom: 1px solid var(--border);
  padding-block: 1rem;
}
.faq-item summary {
  cursor: pointer;
  font-weight: 700;
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  list-style: none;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  font-size: 1.3rem; color: var(--accent); flex-shrink: 0;
}
.faq-item[open] summary::after { content: "–"; }
.faq-item p { margin-top: .6rem; color: var(--ink-soft); }

/* ==========================================================================
   11. More tools
   ========================================================================== */
.more-tools { padding-block: 1rem 3rem; }
.more-tools h2 { font-size: clamp(1.25rem, 3vw, 1.55rem); margin-bottom: 1.25rem; }
.more-tools__grid { display: grid; gap: 1rem; }
@media (min-width: 720px) { .more-tools__grid { grid-template-columns: repeat(3, minmax(0,1fr)); } }
.more-tools__card {
  position: relative;
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1.1rem;
  transition: border-color .15s var(--ease-out), transform .15s var(--ease-out);
}
.more-tools__card:hover { border-color: var(--accent); transform: translateY(-2px); }
.more-tools__card h3 { font-size: .98rem; margin-bottom: .4rem; color: var(--accent); }
.more-tools__card p { font-size: .87rem; color: var(--ink-soft); }
.more-tools__card--soon { opacity: .75; }
.badge-soon {
  display: inline-block; margin-top: .7rem;
  font-size: .72rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em;
  color: var(--cta); border: 1px solid var(--cta); border-radius: 999px;
  padding: .2rem .55rem;
}

/* Sub-tool pages (Ohm / resistencias / AWG) */
.subtool-back { display: inline-flex; align-items: center; gap: .4rem; color: var(--accent); font-weight: 700; font-size: .9rem; margin-bottom: 1rem; }
.subtool-back svg { width: 16px; height: 16px; }
.ohm-grid { display: grid; gap: .85rem; grid-template-columns: repeat(2, minmax(0,1fr)); }
@media (min-width: 560px) { .ohm-grid { grid-template-columns: repeat(4, minmax(0,1fr)); } }
.ohm-field { display: flex; flex-direction: column; gap: .35rem; min-width: 0; }
.ohm-field__label { font-size: .8rem; font-weight: 700; color: var(--ink-soft); }
.ohm-field input {
  width: 100%; box-sizing: border-box;
  padding: .7rem .8rem; border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg); font-family: var(--mono); font-weight: 600; font-size: 1rem;
}
.ohm-field input:focus { border-color: var(--accent); }
.ohm-field input[data-computed="true"] { background: var(--accent-soft); border-color: var(--accent); }
.ohm-actions { display: flex; gap: .7rem; margin-top: 1rem; flex-wrap: wrap; }
.btn-primary, .btn-secondary {
  padding: .7rem 1.1rem; border-radius: var(--radius-sm); font-weight: 700; font-size: .92rem;
}
.btn-primary { background: var(--cta); color: var(--cta-ink); }
.btn-primary:hover { background: var(--cta-dark); }
.btn-secondary { border: 1.5px solid var(--border); color: var(--ink-soft); }
.btn-secondary:hover { border-color: var(--accent); color: var(--ink); }
.ohm-hint { margin-top: .9rem; font-size: .85rem; color: var(--ink-soft); }

.resistor-visual { display: flex; justify-content: center; margin-block: 1.25rem; }
.resistor-visual svg { width: 220px; height: auto; }
.band-row { display: grid; gap: .75rem; grid-template-columns: repeat(2, minmax(0,1fr)); margin-bottom: 1rem; }
@media (min-width: 560px) { .band-row { grid-template-columns: repeat(4, minmax(0,1fr)); } }
.band-field { display: flex; flex-direction: column; gap: .35rem; min-width: 0; }
.band-field__label { font-size: .8rem; font-weight: 700; color: var(--ink-soft); }
.band-field select {
  width: 100%; box-sizing: border-box;
  padding: .65rem .7rem; border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg); font-weight: 600;
}

.awg-grid { display: grid; gap: .85rem; grid-template-columns: minmax(0,1fr); }
@media (min-width: 640px) { .awg-grid { grid-template-columns: minmax(0,1fr) minmax(0,1fr); } }
.awg-field { min-width: 0; display: flex; flex-direction: column; gap: .35rem; }
.awg-field select, .awg-field input {
  width: 100%; box-sizing: border-box;
  padding: .75rem .85rem; border: 1.5px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg); font-size: 1.02rem; font-weight: 600;
}
.awg-result-grid { display: grid; gap: .75rem; grid-template-columns: repeat(2, 1fr); margin-top: 1rem; }
.awg-result-card { background: var(--accent-soft); border: 1px solid var(--accent); border-radius: var(--radius-sm); padding: .85rem; text-align: center; }
.awg-result-card__label { font-size: .78rem; font-weight: 700; color: var(--ink-soft); text-transform: uppercase; }
.awg-result-card__value { font-family: var(--mono); font-size: 1.3rem; font-weight: 700; margin-top: .3rem; }

/* ==========================================================================
   12. Download interstitial dialog
   ========================================================================== */
.download-dialog {
  border: none; border-radius: var(--radius);
  padding: 1.5rem;
  max-width: 380px; width: calc(100% - 2rem);
  box-shadow: var(--shadow-md);
  background: var(--surface);
  color: var(--ink);
}
.download-dialog::backdrop { background: rgba(16, 26, 31, .55); }
.download-dialog__close {
  position: absolute; top: .6rem; right: .6rem;
  width: 32px; height: 32px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--bg);
  font-size: 1rem;
}
.download-dialog__note { margin-top: 1rem; font-weight: 600; text-align: center; }
.download-dialog__cta {
  margin-top: 1rem; width: 100%;
  padding: .75rem; border-radius: var(--radius-sm);
  background: var(--accent); color: var(--accent-ink);
  font-weight: 700; text-align: center;
}

/* ==========================================================================
   13. Corner toast
   ========================================================================== */
.corner-toast {
  position: fixed; right: 1rem; bottom: 1rem; z-index: 30;
  width: min(260px, calc(100vw - 2rem));
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
  padding: .6rem;
  animation: toast-in .4s var(--ease-out);
}
@keyframes toast-in { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .corner-toast { animation: none; } }
.corner-toast__close {
  position: absolute; top: -8px; right: -8px;
  width: 24px; height: 24px; border-radius: 50%;
  background: var(--ink); color: var(--bg);
  display: grid; place-items: center; font-size: .75rem;
}

/* ==========================================================================
   14. Reduced motion global
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  * { animation-duration: .001ms !important; transition-duration: .001ms !important; }
}