/* ============================================================
   Binary Calculator — Stylesheet
   Design tokens, base styles and component styles live here.
   Breakpoint-specific overrides live in responsive.css
   ============================================================ */

/* ---------- Design tokens ---------- */
:root {
  /* Color */
  --color-bg: #F8FAFC;
  --color-surface: #FFFFFF;
  --color-border: #E5E9F0;
  --color-border-strong: #CBD5E1;

  --color-primary: #2563EB;
  --color-primary-hover: #1D4ED8;
  --color-primary-tint: #EFF4FF;
  --color-primary-tint-strong: #DCE7FE;

  --color-text: #0F172A;
  --color-text-soft: #475569;
  --color-text-faint: #94A3B8;

  --color-success: #059669;
  --color-success-tint: #ECFDF5;
  --color-danger: #DC2626;
  --color-danger-tint: #FEF2F2;

  /* Type */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'SFMono-Regular', Consolas, monospace;

  /* Radius */
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --radius-pill: 999px;

  /* Shadow */
  --shadow-soft: 0 1px 2px rgba(15, 23, 42, 0.04), 0 8px 24px -8px rgba(15, 23, 42, 0.08);
  --shadow-lift: 0 4px 10px rgba(15, 23, 42, 0.05), 0 16px 36px -12px rgba(37, 99, 235, 0.18);
  --shadow-ring: 0 0 0 4px var(--color-primary-tint-strong);

  /* Motion */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --dur-fast: 150ms;
  --dur-base: 220ms;
  --dur-slow: 420ms;

  /* Layout */
  --container-w: 1120px;
}

/* ---------- Reset ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
  min-height: 100vh;
  font-feature-settings: 'cv02', 'cv03', 'cv04', 'cv11';
  -webkit-font-smoothing: antialiased;
}

img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; }
ul, ol { list-style: none; }
input, select, button { font-family: inherit; font-size: inherit; color: inherit; }

/* Visible keyboard focus everywhere */
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

.container {
  max-width: var(--container-w);
  margin-inline: auto;
  padding-inline: 24px;
}

/* ============================================================
   HEADER
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(248, 250, 252, 0.85);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 32px;
  height: 72px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 16.5px;
  letter-spacing: -0.01em;
  white-space: nowrap;
}

.brand-icon {
  font-size: 20px;
  line-height: 1;
  transform: translateY(-1px);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 4px;
  flex: 1;
}

.nav-link {
  position: relative;
  padding: 8px 14px;
  border-radius: var(--radius-pill);
  font-size: 14.5px;
  font-weight: 500;
  color: var(--color-text-soft);
  transition: color var(--dur-fast) var(--ease-out), background var(--dur-fast) var(--ease-out);
}

.nav-link:hover {
  color: var(--color-text);
  background: rgba(15, 23, 42, 0.04);
}

.nav-link.is-active {
  color: var(--color-primary);
  background: var(--color-primary-tint);
}

.header-social {
  display: flex;
  align-items: center;
  gap: 4px;
}

.social-link {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 12px;
  border-radius: var(--radius-pill);
  font-size: 13.5px;
  font-weight: 500;
  color: var(--color-text-soft);
  transition: color var(--dur-fast) var(--ease-out), background var(--dur-fast) var(--ease-out);
}

.social-link:hover {
  color: var(--color-primary);
  background: var(--color-primary-tint);
}

.social-link .icon {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  width: 36px;
  height: 36px;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
}

.nav-toggle span {
  display: block;
  height: 2px;
  width: 20px;
  margin-inline: auto;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform var(--dur-base) var(--ease-out), opacity var(--dur-base) var(--ease-out);
}

/* ============================================================
   MAIN / HERO HEADING
   ============================================================ */
.page-inner {
  padding-block: 56px 96px;
}

.page-heading {
  max-width: 620px;
  margin-bottom: 44px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--color-primary);
  background: var(--color-primary-tint);
  padding: 5px 12px;
  border-radius: var(--radius-pill);
  margin-bottom: 18px;
}

.page-heading h1 {
  font-size: clamp(30px, 4vw, 40px);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 14px;
}

.page-sub {
  font-size: 16px;
  color: var(--color-text-soft);
  line-height: 1.6;
}

/* ============================================================
   WORKSPACE / CARDS
   ============================================================ */
.workspace {
  display: grid;
  grid-template-columns: minmax(0, 420px) minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-soft);
  padding: 32px;
  transition: box-shadow var(--dur-base) var(--ease-out), transform var(--dur-base) var(--ease-out);
}

.card:hover {
  box-shadow: var(--shadow-lift);
  transform: translateY(-2px);
}

.card-head {
  margin-bottom: 24px;
}

.card-head h2 {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
}

.card-subtext {
  font-size: 13.5px;
  color: var(--color-text-faint);
}

/* ---------- Fields ---------- */
.field-group {
  margin-bottom: 20px;
}

.field-group label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--color-text-soft);
  margin-bottom: 8px;
  letter-spacing: -0.005em;
}

.bit-input-wrap {
  position: relative;
}

.bit-input {
  width: 100%;
  height: 52px;
  padding: 0 44px 0 16px;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  background: #FCFDFE;
  font-family: var(--font-mono);
  font-size: 17px;
  font-weight: 500;
  letter-spacing: 0.12em;
  color: var(--color-text);
  transition: border-color var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-base) var(--ease-out),
              background var(--dur-fast) var(--ease-out);
}

.bit-input::placeholder {
  color: var(--color-text-faint);
  letter-spacing: 0.04em;
  font-weight: 400;
}

.bit-input:hover {
  border-color: var(--color-border-strong);
}

.bit-input:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
  box-shadow: var(--shadow-ring);
}

.bit-input.is-valid {
  border-color: var(--color-success);
}

.bit-input.is-invalid {
  border-color: var(--color-danger);
}

.bit-input-status {
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%) scale(0.6);
  width: 20px;
  height: 20px;
  border-radius: 50%;
  opacity: 0;
  transition: opacity var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out);
  pointer-events: none;
}

.bit-input-status.show {
  opacity: 1;
  transform: translateY(-50%) scale(1);
}

.bit-input-status.valid {
  background: var(--color-success-tint) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath d='M5 13l4 4L19 7' stroke='%23059669' stroke-width='2.4' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E") center/12px no-repeat;
}

.bit-input-status.invalid {
  background: var(--color-danger-tint) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath d='M6 6l12 12M18 6L6 18' stroke='%23DC2626' stroke-width='2.4' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E") center/12px no-repeat;
}

.field-error {
  min-height: 18px;
  font-size: 12.5px;
  color: var(--color-danger);
  margin-top: 6px;
  opacity: 0;
  transform: translateY(-2px);
  transition: opacity var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out);
}

.field-error.show {
  opacity: 1;
  transform: translateY(0);
}

.field-hint {
  font-size: 12.5px;
  color: var(--color-text-faint);
  margin-top: 8px;
}

/* ---------- Select ---------- */
.select-wrap {
  position: relative;
}

.select-wrap select {
  width: 100%;
  height: 52px;
  padding: 0 40px 0 16px;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  background: #FCFDFE;
  font-size: 14.5px;
  font-weight: 500;
  appearance: none;
  -webkit-appearance: none;
  transition: border-color var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-base) var(--ease-out),
              background var(--dur-fast) var(--ease-out);
}

.select-wrap select:hover {
  border-color: var(--color-border-strong);
}

.select-wrap select:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
  box-shadow: var(--shadow-ring);
}

.select-chevron {
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%);
  width: 18px;
  height: 18px;
  color: var(--color-text-faint);
  pointer-events: none;
}

/* ---------- Buttons ---------- */
.button-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 28px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  height: 46px;
  padding: 0 20px;
  border: none;
  border-radius: var(--radius-md);
  font-size: 14.5px;
  font-weight: 600;
  letter-spacing: -0.005em;
  transition: background var(--dur-fast) var(--ease-out),
              color var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out),
              transform var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-fast) var(--ease-out);
}

.btn:active {
  transform: scale(0.97);
}

.btn .icon {
  width: 16px;
  height: 16px;
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
  box-shadow: 0 1px 2px rgba(37, 99, 235, 0.15), 0 8px 20px -6px rgba(37, 99, 235, 0.45);
  flex: 1;
}

.btn-primary:hover {
  background: var(--color-primary-hover);
  box-shadow: 0 1px 2px rgba(37, 99, 235, 0.2), 0 10px 24px -6px rgba(37, 99, 235, 0.55);
  transform: translateY(-1px);
}

.btn-ghost {
  background: var(--color-surface);
  color: var(--color-text);
  border: 1.5px solid var(--color-border);
}

.btn-ghost:hover {
  border-color: var(--color-border-strong);
  background: #F8FAFC;
}

.btn-text {
  background: transparent;
  color: var(--color-text-soft);
  padding-inline: 12px;
}

.btn-text:hover {
  color: var(--color-danger);
}

/* ============================================================
   RESULT CARD
   ============================================================ */
.result-card {
  min-height: 100%;
}

.result-empty {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 14px;
  padding: 56px 24px;
  color: var(--color-text-faint);
  text-align: center;
}

.empty-icon {
  width: 40px;
  height: 40px;
  color: var(--color-border-strong);
}

.result-empty p {
  font-size: 14px;
  max-width: 260px;
}

.result-body {
  animation: resultFade var(--dur-slow) var(--ease-out);
}

@keyframes resultFade {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.result-row {
  padding: 18px 0;
  border-bottom: 1px solid var(--color-border);
}

.result-row:first-child {
  padding-top: 0;
}

.result-label-line {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
}

.result-label {
  font-size: 12.5px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--color-text-faint);
}

.copy-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 30px;
  height: 30px;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
  color: var(--color-text-faint);
  transition: background var(--dur-fast) var(--ease-out), color var(--dur-fast) var(--ease-out);
}

.copy-btn:hover {
  background: var(--color-primary-tint);
  color: var(--color-primary);
}

.copy-btn svg {
  width: 15px;
  height: 15px;
}

.result-value {
  font-size: 22px;
  font-weight: 600;
  letter-spacing: 0.02em;
  word-break: break-all;
}

.mono {
  font-family: var(--font-mono);
}

/* Grouped binary readout: subtle nibble separation */
#resBinary {
  line-height: 1.5;
}

.steps-block {
  margin-top: 28px;
  padding-top: 24px;
  border-top: 1px dashed var(--color-border);
}

.steps-block h3 {
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-faint);
  margin-bottom: 14px;
}

.steps-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.steps-list li {
  display: flex;
  gap: 12px;
  font-size: 13.5px;
  color: var(--color-text-soft);
  padding: 12px 14px;
  background: #F8FAFC;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  line-height: 1.55;
}

.steps-list .step-index {
  flex-shrink: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  color: var(--color-primary);
  background: var(--color-primary-tint);
  width: 22px;
  height: 22px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

.steps-list code {
  font-family: var(--font-mono);
  background: var(--color-primary-tint);
  color: var(--color-primary-hover);
  padding: 1px 6px;
  border-radius: 5px;
  font-size: 12.5px;
}

/* ============================================================
   TOAST
   ============================================================ */
.toast {
  position: fixed;
  left: 50%;
  bottom: 32px;
  transform: translate(-50%, 16px);
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 20px;
  background: var(--color-text);
  color: #fff;
  font-size: 13.5px;
  font-weight: 500;
  border-radius: var(--radius-pill);
  box-shadow: 0 10px 30px -6px rgba(15, 23, 42, 0.35);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--dur-base) var(--ease-out), transform var(--dur-base) var(--ease-out);
  z-index: 100;
  white-space: nowrap;
}

.toast.show {
  opacity: 1;
  transform: translate(-50%, 0);
}

/* ============================================================
   FOOTER
   ============================================================ */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding-block: 28px;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  font-size: 13.5px;
  color: var(--color-text-soft);
}

.footer-credit .heart {
  display: inline-block;
  animation: heartbeat 1.8s ease-in-out infinite;
}

@keyframes heartbeat {
  0%, 100% { transform: scale(1); }
  15% { transform: scale(1.18); }
  30% { transform: scale(1); }
  45% { transform: scale(1.12); }
  60% { transform: scale(1); }
}

.footer-links {
  display: flex;
  align-items: center;
  gap: 10px;
}

.footer-links a {
  color: var(--color-text-soft);
  transition: color var(--dur-fast) var(--ease-out);
}

.footer-links a:hover {
  color: var(--color-primary);
}

.footer-dot {
  color: var(--color-text-faint);
}