:root {
    /* Responsive sizing variables */
    --rod-height: clamp(140px, 28vh, 220px);
    --rod-width: clamp(32px, 8vw, 56px);
    --bead: clamp(16px, 3.8vw, 26px);
    /* Distance a bead travels to touch the center bar: half rod height minus bead height */
    --bead-shift: calc(var(--rod-height) / 2 - var(--bead));
    --center-bar: clamp(2px, 0.5vh, 4px);
    --label-gap: clamp(2.5rem, 6vh, 5.5rem);
    --abacus-padding: clamp(0.5rem, 2.5vw, 1rem);
    --container-padding: clamp(1rem, 4vw, 2rem);
    --rod-margin-x: clamp(0.25rem, 1.5vw, 1rem);
    /* Size of the triad separator dot on the center bar */
    --group-dot: clamp(6px, 1.5vw, 10px);
    /* Vertical offset for power labels (top and bottom) */
    --power-label-offset: clamp(4rem, 5vh, 5.5rem);
    /* Minimum height reserved for the math notation line (prevents layout shift) */
    --notation-minh: clamp(1.8rem, 3.5vh, 2.6rem);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Helvetica Neue', Arial, 'Noto Sans', 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol', sans-serif;
    background-color: #1a202c;
    color: #e2e8f0;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 1rem;
}

.container {
    display: flex;
    flex-direction: column;
    align-items: center;
    background-color: #2d3748;
    border-radius: 1rem;
    padding: var(--container-padding);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    width: 100%;
    max-width: 600px;
    position: relative;
}

.abacus {
    display: flex;
    align-items: flex-end;
    /* Reserve vertical space above for top decimal labels so they don't overlap the description */
    margin-top: var(--power-label-offset);
    margin-bottom: 2rem;
    position: relative;
    background-color: #4a5568;
    /* Soroban-inspired heaven/earth subtle cue */
    background-image: linear-gradient(to bottom, rgba(255,255,255,0.04) 0 50%, rgba(0,0,0,0.08) 50% 100%);
    border: 4px solid #718096;
    border-radius: 0.5rem;
    padding: var(--abacus-padding);
}

.center-bar {
    position: absolute;
    top: 50%;
    left: 0;
    right: 0;
    height: var(--center-bar);
    background-color: #e2e8f0;
    transform: translateY(-50%);
}

.rod {
    display: flex;
    flex-direction: column;
    align-items: center;
    height: var(--rod-height);
    width: var(--rod-width);
    position: relative;
    margin: 0 var(--rod-margin-x);
}

.rod-line {
    position: absolute;
    height: 100%;
    width: clamp(1px, 0.3vw, 2px);
    background-color: #a0aec0;
    left: 50%;
    transform: translateX(-50%);
}

.bead {
    width: 0;
    height: 0;
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    cursor: pointer;
    transition: transform 0.3s ease-in-out;
}

.bead.top {
    top: 0;
    border-left: var(--bead) solid transparent;
    border-right: var(--bead) solid transparent;
    border-top: var(--bead) solid #48bb78;
}

.bead.bottom {
    bottom: 0;
    border-left: var(--bead) solid transparent;
    border-right: var(--bead) solid transparent;
    border-bottom: var(--bead) solid #48bb78;
}

.bead.top.active {
    transform: translate(-50%, var(--bead-shift));
    border-top-color: #38a169;
}

.bead.bottom.active {
    transform: translate(-50%, calc(-1 * var(--bead-shift)));
    border-bottom-color: #c53030;
}

.power-label {
    position: absolute;
    bottom: calc(-1 * var(--power-label-offset));
    font-size: 0.875rem;
    color: #a0aec0;
    text-align: center;
    width: 100%;
}

.power-label-top {
    position: absolute;
    top: calc(-1 * var(--power-label-offset));
    font-size: 0.875rem;
    color: #a0aec0;
    text-align: center;
    width: 100%;
}

.abacus-value {
    font-size: 1.5rem;
    font-weight: bold;
    margin-top: 1rem;
    text-align: center;
}

/* Reserve space for MathJax notation to avoid flicker/reflow when it appears */
#math-notation {
    min-height: var(--notation-minh);
    line-height: 1.4;
}

.value-labels {
    position: absolute;
    right: -2rem;
    top: 50%;
    transform: translateY(-50%);
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: var(--label-gap);
}

.value-labels span {
    font-size: clamp(0.9rem, 2.8vw, 1.25rem);
    font-weight: bold;
    color: #e2e8f0;
}

/* Soroban-inspired grouping every 3 rods for readability:
   Replace vertical line with a centered black dot on the center bar */
#abacus-rods-container .rod:nth-child(3n+1) {
    /* keep a little spacing for readability */
    padding-left: clamp(0.25rem, 1.2vw, 0.5rem);
}
#abacus-rods-container .rod:nth-child(3n+1)::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 0;
    width: var(--group-dot);
    height: var(--group-dot);
    background: rgb(0,92,220);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    z-index: 2;
    pointer-events: none;
}

.translation-button {
    position: fixed !important;
    top: calc(0.75rem + env(safe-area-inset-top, 0px)) !important;
    left: calc(0.75rem + env(safe-area-inset-left, 0px)) !important;
    background-color: #4a5568;
    color: #e2e8f0;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    cursor: pointer;
    font-weight: bold;
    transition: background-color 0.2s;
    z-index: 2147483647; /* ensure always on top */
    pointer-events: auto;
}

.translation-button:hover {
    background-color: #6a768c;
}

.triquetra-logo {
    width: clamp(120px, 25vw, 200px);
    height: auto;
    margin-bottom: 5rem;
    max-width: 100%;
}

/* Reserve space on the left so the centered title doesn't sit under the EN button */
#main-title {
    padding-left: clamp(3rem, 12vw, 6rem);
}
/* Fixed GitHub link at top-right of the page */
.github-link {
    position: fixed !important;
    top: calc(0.75rem + env(safe-area-inset-top, 0px)) !important;
    right: calc(0.75rem + env(safe-area-inset-right, 0px)) !important;
    color: #e2e8f0;
    opacity: 0.9;
    z-index: 2147483647; /* ensure always on top */
    transition: color 0.2s ease, opacity 0.2s ease;
    pointer-events: auto;
}
.github-link:hover {
    color: #63b3ed;
    opacity: 1;
}
.github-link svg {
    width: clamp(22px, 3.5vw, 28px);
    height: clamp(22px, 3.5vw, 28px);
    display: block;
}

/* ====== Top controls + menu ====== */
:root {
  --topbar-bg: rgba(17, 24, 39, 0.7); /* cinza-900 com transparência */
  --topbar-text: #e5e7eb;             /* cinza-200 */
  --topbar-border: rgba(255,255,255,0.08);
  --topbar-height: 56px; /* altura aproximada da barra superior (botões 36px + padding 10px) */
  --menu-bg: #111827;                 /* cinza-900 */
  --menu-border: rgba(255,255,255,0.12);
  --menu-shadow: 0 8px 24px rgba(0,0,0,0.3);
  --menu-item: #e5e7eb;
  --menu-item-muted: #9ca3af;         /* cinza-400 */
  --menu-item-hover: #34d399;         /* teal-400 */
  --focus-ring: 0 0 0 3px rgba(52, 211, 153, 0.45);
}

body.dark {
  /* Mantém as cores similares, mas pode ser ajustado conforme seu tema */
  --topbar-bg: rgba(17, 24, 39, 0.75);
  --topbar-text: #e5e7eb;
  --topbar-border: rgba(255,255,255,0.12);
  --menu-bg: #0b1220;
  --menu-border: rgba(255,255,255,0.16);
  --menu-item: #e5e7eb;
  --menu-item-muted: #9ca3af;
  --menu-item-hover: #5eead4; /* teal-300 */
}

.top-controls {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 14px;
  background: var(--topbar-bg);
  color: var(--topbar-text);
  backdrop-filter: saturate(120%) blur(6px);
  -webkit-backdrop-filter: saturate(120%) blur(6px);
  border-bottom: 1px solid var(--topbar-border);
  z-index: 2147483646; /* below legacy fixed buttons we will hide */
}

.language-switcher select {
  appearance: none;
  background: transparent;
  color: var(--topbar-text);
  border: 1px solid var(--topbar-border);
  border-radius: 8px;
  padding: 6px 10px;
  font-size: 14px;
}
.language-switcher select:focus {
  outline: none;
  box-shadow: var(--focus-ring);
}

.right-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}

.icon-button,
.github-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 10px;
  border: 1px solid var(--topbar-border);
  background: transparent;
  color: var(--topbar-text);
  cursor: pointer;
  text-decoration: none;
}
.icon-button:hover,
.github-button:hover {
  background: rgba(255,255,255,0.06);
}
.icon-button:focus-visible,
.github-button:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.menu-wrapper { position: relative; }
.menu-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 260px;
  padding: 8px;
  background: var(--menu-bg);
  border: 1px solid var(--menu-border);
  border-radius: 12px;
  box-shadow: var(--menu-shadow);
}
.menu-item {
  display: block;
  padding: 10px 12px;
  border-radius: 8px;
  color: var(--menu-item);
  text-decoration: none;
  font-size: 14px;
}
.menu-item:hover,
.menu-item:focus {
  background: rgba(255,255,255,0.06);
  color: var(--menu-item-hover);
}

/* Utilitários de acessibilidade */
.visually-hidden {
  position: absolute !important;
  height: 1px; width: 1px;
  overflow: hidden; clip: rect(1px, 1px, 1px, 1px);
  white-space: nowrap; clip-path: inset(50%);
}

/* Responsividade básica */
@media (max-width: 480px) {
  .menu-dropdown {
    min-width: 220px;
  }
}

/* Hide legacy floating controls to avoid overlap with new top bar */
.github-link,
.translation-button {
  display: none !important;
}

/* Reserve space for the fixed top bar so content (e.g., logo) isn't hidden underneath */
body {
  padding-top: calc(var(--topbar-height) + 8px + env(safe-area-inset-top, 0px));
}



/* ===== Light theme overrides ===== */
body.light {
  /* Page base colors */
  background-color: #f8fafc; /* slate-50 */
  color: #111827; /* gray-900 */
}

/* Light theme variables for top bar and menu */
body.light {
  --topbar-bg: rgba(255, 255, 255, 0.75);
  --topbar-text: #111827; /* gray-900 */
  --topbar-border: rgba(0, 0, 0, 0.12);
  --menu-bg: #ffffff;
  --menu-border: rgba(0, 0, 0, 0.12);
  --menu-item: #111827;
  --menu-item-muted: #6b7280; /* gray-500 */
  --menu-item-hover: #0f766e; /* teal-800 */
}

/* Component overrides in light mode */
body.light .container {
  background-color: #ffffff;
  color: #111827;
  box-shadow: 0 10px 20px rgba(0,0,0,0.08);
}

body.light .abacus {
  background-color: #e5e7eb; /* gray-200 */
  border-color: #94a3b8; /* slate-400 */
}
body.light .center-bar { background-color: #111827; }
body.light .rod-line { background-color: #64748b; }
body.light .power-label,
body.light .power-label-top { color: #475569; }
body.light .value-labels span { color: #111827; }

/* Common text blocks in light mode */
body.light #main-title,
body.light #total-title,
body.light #footer-sum-title { color: #0f766e; }
body.light #description,
body.light #math-notation,
body.light .text-gray-400,
body.light .text-gray-300 { color: #475569 !important; }

/* Buttons (clear/invert) retain contrast in light mode */
body.light #clear-button,
body.light #invert-button {
  background-color: #e5e7eb; /* gray-200 */
  color: #111827;
  border-color: #cbd5e1; /* slate-300 */
}
body.light #clear-button:hover,
body.light #invert-button:hover {
  background-color: #cbd5e1; /* slate-300 */
}

/* Collapsible sections backgrounds */
body.light #tutorial-content,
body.light #sum-content {
  background-color: #f1f5f9; /* slate-100 */
  color: #111827;
}

/* Override Tailwind utility classes used in HTML so they look good in light */
body.light .bg-gray-800 { background-color: #ffffff !important; }
body.light .bg-gray-700 { background-color: #f1f5f9 !important; }
body.light .text-gray-100 { color: #111827 !important; }
body.light .text-white { color: #111827 !important; }
body.light .text-gray-200 { color: #1f2937 !important; }

/* Triquetra logo spacing unchanged; ensure it contrasts with light bg via surrounding colors */
body.light .triquetra-logo { filter: none; }

/* Top controls buttons inherit text color; ensure hover backgrounds are subtle in light */
body.light .icon-button:hover,
body.light .github-button:hover {
  background: rgba(0,0,0,0.06);
}