* { 
  box-sizing: border-box; 
  -webkit-tap-highlight-color: transparent;
}

html {
  height: 100%;
}

/* Force form elements to inherit Google Sans Flex */
button, input, select {
  font-family: inherit;
}

button:focus {
  outline: none;
}

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

:root {
  --bg: #f4f6f8;
  --card: #ffffff;
  --text: #000000;
  --muted: #666666;
  --divider: rgba(0,0,0,0.12);
  --accent: #1a73e8;
  --input-border: rgba(0,0,0,0.18);
  
  --toggle-bg: #e1e4e8;
  --toggle-active-bg: #ffffff;
  --toggle-active-text: #1a73e8;
  --toggle-shadow: 0 1px 3px rgba(0,0,0,0.12);
  --modal-overlay: rgba(0,0,0,0.4);
  --dropdown-shadow: 0 4px 16px rgba(0,0,0,0.1);
}

[data-theme="dark"] {
  --bg: #0f1115;
  --card: #181b22;
  --text: #f1f3f6;
  --muted: #a0a4ab;
  --divider: rgba(255,255,255,0.12);
  --accent: #4c8dff;
  --input-border: rgba(255,255,255,0.22);
  
  --toggle-bg: #2a2e38;
  --toggle-active-bg: #181b22;
  --toggle-active-text: #4c8dff;
  --toggle-shadow: 0 1px 3px rgba(0,0,0,0.3);
  --modal-overlay: rgba(0,0,0,0.7);
  --dropdown-shadow: 0 4px 16px rgba(0,0,0,0.4);
}

body {
  margin: 0;
  /* Updated to prioritize Google Sans Flex */
  font-family: "Google Sans Flex", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  padding: 24px;
  transition: background 0.45s ease, color 0.45s ease;
}

.wrapper {
  margin: auto;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.page-title {
  font-size: 28px;
  font-weight: 800;
  text-align: center;
  margin: 0 0 16px 0;
  max-width: 700px;
  line-height: 1.3;
  color: var(--text);
  transition: color 0.45s ease;
}

.page-subtitle {
  font-size: 16px;
  font-weight: 400;
  text-align: center;
  margin: 0 0 32px 0;
  max-width: 680px;
  line-height: 1.6;
  color: var(--muted);
  transition: color 0.45s ease;
}

.currency-toggle-wrapper {
  margin-bottom: 32px;
}

.currency-toggle-container {
  display: flex;
  background: var(--toggle-bg);
  border-radius: 10px;
  padding: 4px;
  border: 1px solid var(--divider);
}

.currency-toggle-btn {
  padding: 10px 24px;
  font-size: 14px;
  font-weight: 500; 
  border-radius: 8px; 
  border: none;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  text-align: center;
  min-width: 100px;
}

@media (hover: hover) {
  .currency-toggle-btn:hover:not(.active) {
    color: var(--text);
  }
}

.currency-toggle-btn.active {
  background: var(--toggle-active-bg);
  color: var(--toggle-active-text);
  box-shadow: var(--toggle-shadow);
}

.card {
  background: var(--card);
  padding: 40px;
  border-radius: 20px;
  box-shadow: 0 12px 40px rgba(0,0,0,0.12);
  width: 100%;
  max-width: 640px;
  text-align: center;
  transition: background 0.45s ease;
}

h2 {
  margin: 0;
  font-size: 30px;
  font-weight: 700;
}

.as-of {
  margin-top: 8px;
  font-size: 14px;
  color: var(--muted);
}

.header-divider,
.divider {
  height: 1px;
  background: var(--divider);
  margin: 24px 0;
  transition: background 0.45s ease;
}

.rate-block { 
  margin-bottom: 24px; 
}

.rate-block:last-of-type {
  margin-bottom: 0; 
}

.rate-label {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--muted);
  margin-bottom: 8px;
}

.rate-value {
  font-size: 26px;
  font-weight: 700;
}

.rate-value.highlight {
  color: var(--accent);
}

.section-label {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 24px;
}

.input-group {
  position: relative;
  width: 100%;
}

input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 
}
input[type=number] {
  -moz-appearance: textfield;
}

input {
  width: 100%;
  padding: 16px 50px 16px 16px; 
  font-size: 18px;
  border-radius: 12px;
  border: 1px solid var(--input-border);
  background: transparent;
  color: var(--text);
  transition: border-color 0.35s ease, background 0.35s ease;
}

input::placeholder { color: var(--muted); }

input:focus {
  outline: none;
  border-color: var(--accent);
}

.spin-btns {
  position: absolute;
  right: 1px;
  top: 1px;
  bottom: 1px;
  display: flex;
  flex-direction: column;
  width: 40px;
  border-left: 1px solid var(--input-border);
  border-radius: 0 12px 12px 0;
  overflow: hidden;
}

.spin-btn {
  flex: 1;
  border: none;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s, color 0.2s;
  padding: 0;
}

@media (hover: hover) {
  .spin-btn:hover {
    background: rgba(127,127,127,0.1);
    color: var(--text);
  }
}

.spin-btn:active {
  background: rgba(127,127,127,0.2);
}

.spin-btn:first-child {
  border-bottom: 1px solid var(--input-border);
}

input:focus + .spin-btns {
  border-color: var(--accent);
}

input:focus + .spin-btns .spin-btn:first-child {
  border-bottom-color: var(--accent);
}

.result {
  margin-top: 32px;
  font-size: 24px;
  font-weight: 700;
  color: var(--accent);
  min-height: 29px;
  display: block;
}

.placeholder-text {
  font-size: 16px;
  font-weight: 400;
  color: var(--muted);
  opacity: 0.8;
}

.theme-toggle {
  margin-top: 40px;
}

.toggle-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  font-size: 14px;
  border-radius: 999px;
  border: 1px solid var(--divider);
  background: transparent;
  color: var(--text);
  cursor: pointer;
  transition: background 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

@media (hover: hover) {
  .toggle-btn:hover {
    background: rgba(127,127,127,0.08);
  }
}

.modal-overlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: var(--modal-overlay);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  opacity: 1;
  transition: opacity 0.3s ease;
}

.modal-overlay.hidden {
  opacity: 0;
  pointer-events: none;
}

.modal-card {
  background: var(--card);
  padding: 24px 32px;
  border-radius: 16px;
  width: 90%;
  max-width: 420px;
  box-shadow: 0 12px 40px rgba(0,0,0,0.2);
  transform: translateY(0);
  transition: transform 0.3s ease, background 0.45s ease;
}

.modal-overlay.hidden .modal-card {
  transform: translateY(20px);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}

.modal-header h3 {
  margin: 0;
  font-size: 20px;
  font-weight: 700;
}

.close-btn {
  background: transparent;
  border: none;
  font-size: 28px;
  line-height: 1;
  color: var(--muted);
  cursor: pointer;
  padding: 0;
  transition: color 0.2s;
}

@media (hover: hover) {
  .close-btn:hover {
    color: var(--text);
  }
}

.setting-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 0;
  border-bottom: 1px solid var(--divider);
}

.setting-item:last-child {
  border-bottom: none;
}

.setting-label {
  font-size: 15px;
  font-weight: 500;
  color: var(--text);
}

.custom-select-wrapper {
  position: relative;
  width: 130px;
  user-select: none;
}

.custom-select-trigger {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 14px;
  border-radius: 8px;
  border: 1px solid var(--input-border);
  background: var(--card);
  color: var(--text);
  font-size: 14px;
  cursor: pointer;
  transition: border-color 0.2s ease, background 0.2s ease;
}

.custom-select-wrapper.open .custom-select-trigger {
  border-color: var(--accent);
}

.custom-select-trigger svg {
  transition: transform 0.3s ease;
}

.custom-select-wrapper.open .custom-select-trigger svg {
  transform: rotate(180deg);
}

.custom-options {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background: var(--card);
  border: 1px solid var(--input-border);
  border-radius: 8px;
  margin-top: 6px;
  box-shadow: var(--dropdown-shadow);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-8px);
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  z-index: 10;
  overflow: hidden;
}

.custom-select-wrapper.open .custom-options {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.custom-option {
  display: block;
  padding: 10px 14px;
  font-size: 14px;
  color: var(--text);
  cursor: pointer;
  transition: background 0.2s ease;
}

@media (hover: hover) {
  .custom-option:hover {
    background: var(--toggle-bg);
  }
}

.custom-option.selected {
  color: var(--accent);
  font-weight: 600;
  background: var(--toggle-bg);
}

.modal-footer {
  margin-top: 32px;
  display: flex;
  justify-content: flex-end;
}

.btn-save {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 10px 24px;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.2s, transform 0.1s;
}

@media (hover: hover) {
  .btn-save:hover {
    opacity: 0.9;
  }
}

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

.footer-link {
  margin-top: 24px;
  font-size: 13px;
  color: var(--muted);
  text-decoration: none;
  transition: color 0.2s ease;
  opacity: 0.8;
}

@media (hover: hover) {
  .footer-link:hover {
    color: var(--accent);
    opacity: 1;
  }
}

@media (max-width: 768px) {
  .page-title { font-size: 22px; padding: 0 10px; }
  .page-subtitle { font-size: 15px; padding: 0 15px; }
  h2 { font-size: 24px; }
  .rate-value { font-size: 20px; }
  .section-label { font-size: 18px; margin-bottom: 20px; }
  input { font-size: 16px; padding-left: 14px; }
  .result { font-size: 20px; margin-top: 28px; }
  .card { padding: 32px 24px; }
  .modal-card { padding: 24px; }
}