/* ===================================================================
   Date Calculator — Cream world + tomato accent design system
   =================================================================== */

:root {
  --bg:           #faf6f1;
  --bg-2:         #f3eee5;
  --surface:      #ffffff;
  --surface-2:    #faf6ed;
  --surface-3:    #eee7d8;
  --border:       #e8dfcc;
  --border-soft:  #f0e9da;
  --text:         #1f1a14;
  --text-2:       #5c5547;
  --text-3:       #6e6557;
  --text-faint:   #b5ac9b;

  --accent:       #e85f4d;
  --accent-2:     #d44a39;
  --accent-soft:  rgba(232, 95, 77, 0.10);
  --accent-glow:  rgba(232, 95, 77, 0.55);

  --r-sm: 8px;
  --r-md: 12px;
  --r-lg: 16px;
  --r-xl: 20px;
  --r-pill: 999px;

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.06);
  --shadow-lg: 0 24px 48px rgba(0,0,0,0.12);

  --font-ui: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI",
             "PingFang TC", "PingFang SC", "Hiragino Sans", "Noto Sans CJK",
             sans-serif;
  --font-mono: "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --transition: 200ms cubic-bezier(0.4, 0, 0.2, 1);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; }
html, body {
  font-family: var(--font-ui);
  background:
    radial-gradient(ellipse 80% 50% at 50% 0%, rgba(255, 235, 220, 0.55) 0%, transparent 70%),
    var(--bg);
  background-attachment: fixed;
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  line-height: 1.55;
}
button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
input, select { font-family: inherit; color: inherit; }
a { color: var(--accent); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--accent-2); }
ul, ol { list-style: none; }
[hidden] { display: none !important; }

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

.skip-link {
  position: absolute;
  left: -9999px; top: 0;
  background: var(--accent);
  color: #fff;
  padding: 10px 16px;
  font-weight: 600;
  border-radius: 0 0 var(--r-sm) 0;
  z-index: 1000;
}
.skip-link:focus { left: 0; }

.app {
  max-width: 880px;
  margin: 0 auto;
  padding: clamp(12px, 3vw, 24px) clamp(12px, 3vw, 24px) 80px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 8px 4px 28px;
}
.brand {
  font-weight: 600;
  font-size: 15px;
  color: var(--text-2);
}
.brand:hover { color: var(--accent); }

.topbar-right {
  display: flex;
  align-items: center;
  gap: 12px;
}
.nav-link {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-3);
  padding: 6px 10px;
  border-radius: var(--r-sm);
  white-space: nowrap;
  transition: background var(--transition), color var(--transition);
}
.nav-link:hover {
  color: var(--accent);
  background: var(--surface-2);
}

.lang-switcher {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  padding: 6px 28px 6px 10px;
  font-size: 13px;
  font-weight: 500;
  color: var(--text);
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 12 12' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M3 5l3 3 3-3' stroke='%237a7973' stroke-width='1.5' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 8px center;
  background-size: 12px;
  transition: border-color var(--transition);
}
.lang-switcher:hover { border-color: var(--text-3); }
.lang-switcher:focus { outline: none; border-color: var(--accent); }

.page-title {
  font-size: clamp(22px, 4vw, 30px);
  font-weight: 700;
  letter-spacing: -0.02em;
  text-align: center;
  margin-bottom: 6px;
}
.page-sub {
  text-align: center;
  font-size: 14px;
  color: var(--text-3);
  margin-bottom: 28px;
}

/* ============ Date picker card ============ */
.date-picker-card {
  max-width: 520px;
  margin: 0 auto 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: 20px 24px;
  box-shadow: var(--shadow-md);
}
.date-row {
  display: flex;
  gap: 16px;
}
.date-field {
  flex: 1;
  min-width: 0;
}
.date-label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-2);
  margin-bottom: 10px;
}
.date-input {
  width: 100%;
  padding: 12px 14px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  font-size: 16px;
  color: var(--text);
  transition: border-color var(--transition);
}
.date-input:focus {
  outline: none;
  border-color: var(--accent);
}
.date-input::-webkit-calendar-picker-indicator {
  cursor: pointer;
  filter: invert(0.45);
}

/* ============ Mode tabs ============ */
.mode-tabs {
  display: flex;
  justify-content: center;
  gap: 4px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-pill);
  padding: 4px;
  width: max-content;
  margin: 0 auto 24px;
  box-shadow: var(--shadow-sm);
}
.mode-tab {
  padding: 14px 18px;
  min-height: 44px;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-3);
  border-radius: var(--r-pill);
  transition: background var(--transition), color var(--transition);
}
.mode-tab:hover { color: var(--text); }
.mode-tab-active {
  background: var(--accent);
  color: #fff;
}
.mode-tab-active:hover { color: #fff; }
.mode-tab:active { transform: scale(0.96); }

/* ============ Add/Subtract panel ============ */
.add-subtract-panel {
  max-width: 520px;
  margin: 0 auto 24px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: 20px 24px;
  box-shadow: var(--shadow-sm);
}
.add-subtract-row {
  display: flex;
  gap: 16px;
  align-items: flex-end;
}
.add-subtract-field {
  flex: 1;
  min-width: 0;
}
.add-subtract-toggle {
  flex: none;
  width: 160px;
}
.amount-input {
  width: 100%;
  padding: 12px 14px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  font-size: 16px;
  color: var(--text);
  transition: border-color var(--transition);
  -moz-appearance: textfield;
}
.amount-input::-webkit-outer-spin-button,
.amount-input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.amount-input:focus { outline: none; border-color: var(--accent); }
.unit-select {
  width: 100%;
  padding: 12px 14px;
  min-height: 44px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  font-size: 16px;
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 12 12' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M3 5l3 3 3-3' stroke='%237a7973' stroke-width='1.5' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  background-size: 12px;
  transition: border-color var(--transition);
}
.unit-select:focus { outline: none; border-color: var(--accent); }

.toggle-group {
  display: flex;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  overflow: hidden;
}
.toggle-btn {
  flex: 1;
  padding: 12px 14px;
  min-height: 44px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-3);
  text-align: center;
  transition: background var(--transition), color var(--transition);
}
.toggle-btn:hover { color: var(--text); background: var(--surface-3); }
.toggle-btn-active {
  background: var(--accent);
  color: #fff;
}
.toggle-btn-active:hover { background: var(--accent); color: #fff; }

/* ============ Result grid ============ */
.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
  max-width: 720px;
  margin: 0 auto 28px;
}
.result-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: 20px 16px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition);
}
.result-item:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}
.result-primary {
  border-color: var(--accent);
  box-shadow: 0 0 0 1px var(--accent), 0 4px 16px rgba(232, 95, 77, 0.12);
}
.result-number {
  display: block;
  font-family: var(--font-mono);
  font-size: clamp(32px, 6vw, 48px);
  font-weight: 700;
  color: var(--accent-2);
  line-height: 1.1;
  margin-bottom: 6px;
  word-break: break-all;
}
.result-label {
  display: block;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--text-3);
  font-weight: 700;
}

/* ============ Business days result ============ */
.business-result {
  max-width: 480px;
  margin: 0 auto 36px;
  background: var(--surface);
  border: 1px solid var(--accent);
  border-radius: var(--r-lg);
  padding: 36px 24px;
  text-align: center;
  box-shadow: 0 0 0 1px var(--accent), 0 4px 16px rgba(232, 95, 77, 0.12);
}
.business-display {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}
.business-number {
  font-family: var(--font-mono);
  font-size: clamp(56px, 12vw, 80px);
  font-weight: 700;
  color: var(--accent-2);
  line-height: 1;
}
.business-labels {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}
.business-main-label {
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}
.business-sub-label {
  font-size: 12px;
  color: var(--text-3);
}

/* ============ Add/Subtract result ============ */
.add-result {
  max-width: 480px;
  margin: 0 auto 36px;
  background: var(--surface);
  border: 1px solid var(--accent);
  border-radius: var(--r-lg);
  padding: 36px 24px;
  text-align: center;
  box-shadow: 0 0 0 1px var(--accent), 0 4px 16px rgba(232, 95, 77, 0.12);
}
.add-result-display {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}
.add-result-date {
  font-family: var(--font-mono);
  font-size: clamp(28px, 8vw, 42px);
  font-weight: 700;
  color: var(--accent-2);
  line-height: 1;
}
.add-result-label {
  font-size: 13px;
  color: var(--text-3);
  font-weight: 500;
}
.add-result-details {
  font-size: 13px;
  color: var(--text-2);
}

/* ============ Result actions ============ */
.result-actions {
  display: flex;
  justify-content: flex-end;
  max-width: 720px;
  margin: 0 auto 8px;
}

.result-copy {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--r-sm);
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-3);
  box-shadow: var(--shadow-sm);
  transition: color var(--transition), transform 80ms ease-out, background var(--transition), border-color var(--transition);
  position: relative;
}
.result-copy:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
}
.result-copy:active { transform: translateY(1px); }
.result-copy svg { width: 18px; height: 18px; }
.result-copy .icon-check { display: none; color: var(--accent); }
.result-copy.is-copied .icon-copy { display: none; }
.result-copy.is-copied .icon-check { display: block; }
.result-copy.is-copied {
  color: var(--accent);
  background: var(--accent-soft);
  border-color: var(--accent);
}

/* ============ Info ============ */
.info {
  max-width: 720px;
  margin: 40px auto 0;
  padding: 0 4px;
}
.info h2 {
  font-size: clamp(18px, 4vw, 22px);
  font-weight: 600;
  letter-spacing: -0.015em;
  margin: 26px 0 10px;
  color: var(--text);
}
.info p {
  font-size: 15px;
  color: var(--text-2);
  margin-bottom: 10px;
}

/* ============ Footer ============ */
.site-footer {
  max-width: 720px;
  margin: 56px auto 0;
  padding-top: 24px;
  border-top: 1px solid var(--border-soft);
  text-align: center;
}
.site-footer-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 16px;
  font-size: 13px;
  color: var(--text-3);
}
.site-footer a { color: var(--text-2); }
.site-footer a:hover { color: var(--accent); }
.site-footer .sub {
  margin-top: 8px;
  font-size: 11px;
  color: var(--text-3);
}

@media (max-width: 600px) {
  .topbar { padding: 4px 0 20px; }
  .date-row { flex-direction: column; gap: 16px; }
  .add-subtract-row { flex-direction: column; gap: 14px; }
  .add-subtract-toggle { width: 100%; }
}

@media (max-width: 480px) {
  .result-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
  }
  .result-item { padding: 16px 10px; }
  .result-number { font-size: 28px; }
  .date-picker-card { padding: 16px; }
  .add-subtract-panel { padding: 16px; }
  .mode-tab { padding: 7px 14px; font-size: 13px; }
}

@media (max-width: 420px) {
  .topbar-right .nav-link { display: none; }
  .topbar-right { gap: 6px; }
  .lang-switcher { max-width: 130px; font-size: 12px; padding: 4px 22px 4px 8px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}