:root {
  --bg-color: #050505;
  --card-bg: rgba(20, 20, 20, 0.8);
  --card-border: rgba(220, 38, 38, 0.2);
  --primary-color: #dc2626;
  /* Red 600 */
  --accent-color: #991b1b;
  /* Red 800 */
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --input-bg: rgba(10, 10, 10, 0.8);
  --success-color: #22c55e;

  --font-main: "Inter", sans-serif;
  --font-display: "Outfit", sans-serif;

  --radius-md: 12px;
  --radius-lg: 20px;

  --shadow-card: 0 10px 30px -10px rgba(220, 38, 38, 0.15);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-main);
  background-image:
    radial-gradient(
      circle at 10% 20%,
      rgba(220, 38, 38, 0.15) 0%,
      transparent 40%
    ),
    radial-gradient(
      circle at 90% 80%,
      rgba(153, 27, 27, 0.15) 0%,
      transparent 40%
    );
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 20px;
  padding-top: calc(20px + env(safe-area-inset-top));
  padding-bottom: calc(20px + env(safe-area-inset-bottom));
  padding-left: calc(20px + env(safe-area-inset-left));
  padding-right: calc(20px + env(safe-area-inset-right));
}

.app-container {
  width: 100%;
  max-width: 600px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* Header */
.main-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 0;
  flex-wrap: wrap;
  gap: 15px;
}

.logo h1 {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.8rem;
  background: linear-gradient(135deg, var(--primary-color), #ef4444);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  text-shadow: 0 0 20px rgba(220, 38, 38, 0.3);
}

.subtitle {
  font-size: 0.85rem;
  color: var(--text-muted);
  display: block;
}

.settings-bar {
  display: flex;
  gap: 10px;
  align-items: center;
  flex-wrap: nowrap;
}

.unit-toggle {
  background: var(--input-bg);
  border-radius: 8px;
  padding: 4px;
  display: flex;
  border: 1px solid var(--card-border);
}

.unit-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 5px 10px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
  transition: all 0.3s ease;
}

.unit-btn.active {
  background: var(--primary-color);
  color: white;
  box-shadow: 0 2px 8px rgba(220, 38, 38, 0.4);
}

.lang-select {
  background: var(--input-bg);
  color: var(--text-main);
  border: 1px solid var(--card-border);
  padding: 6px 10px;
  border-radius: 8px;
  font-size: 0.85rem;
  cursor: pointer;
}

.lang-select:hover {
  border-color: var(--primary-color);
}

.legacy-btn {
  background: linear-gradient(135deg, #ff6b6b, #ff3b3b);
  color: white;
  border: none;
  padding: 6px 15px;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s ease;
  box-shadow: 0 4px 12px rgba(255, 107, 107, 0.3);
}

.legacy-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(255, 107, 107, 0.5);
}

.guide-btn {
  background: transparent;
  color: var(--primary-color);
  border: 1px solid var(--primary-color);
  padding: 6px 15px;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
  transition: all 0.3s ease;
}

.guide-btn:hover {
  background: rgba(220, 38, 38, 0.1);
  box-shadow: 0 4px 12px rgba(220, 38, 38, 0.2);
}

/* Navigation */
.main-nav {
  display: flex;
  background: var(--card-bg);
  backdrop-filter: blur(12px);
  padding: 5px;
  border-radius: var(--radius-md);
  border: 1px solid var(--card-border);
  overflow-x: auto;
  gap: 5px;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
  /* Firefox */
}

.main-nav::-webkit-scrollbar {
  display: none !important;
  width: 0 !important;
  height: 0 !important;
  -webkit-appearance: none;
}

.nav-btn {
  flex: 1 1 auto;
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 10px 2px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 500;
  white-space: nowrap;
  transition: all 0.3s ease;
  text-decoration: none;
  text-align: center;
}

.nav-btn:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.05);
}

.nav-btn.active {
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--accent-color)
  );
  color: white;
  font-weight: 700;
  box-shadow: 0 4px 12px rgba(220, 38, 38, 0.3);
}

/* Main Content */
.content-area {
  position: relative;
  min-height: 400px;
}

.tool-section {
  display: none;
  animation: fadeIn 0.4s ease;
}

.tool-section.active {
  display: block;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

h2 {
  font-family: var(--font-display);
  margin-bottom: 20px;
  font-size: 1.5rem;
  color: var(--text-main);
}

.input-group {
  margin-bottom: 15px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.row {
  display: flex;
  gap: 15px;
}

.half {
  flex: 1;
}

.third {
  flex: 1;
}

label {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-weight: 500;
}

input,
select {
  width: 100%;
  background: var(--input-bg);
  border: 1px solid var(--card-border);
  color: var(--text-main);
  padding: 12px 15px;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-family: var(--font-main);
  transition:
    border-color 0.3s,
    box-shadow 0.3s;
}

input:focus,
select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 2px rgba(220, 38, 38, 0.2);
}

/* Accessibility Focus States */
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

.range-inputs {
  display: flex;
  align-items: center;
  gap: 5px;
}

.range-inputs input {
  width: 100%;
  text-align: center;
}

.action-btn {
  width: 100%;
  padding: 15px;
  background: linear-gradient(135deg, var(--primary-color), #b91c1c);
  border: none;
  border-radius: var(--radius-md);
  color: #fff;
  font-weight: 700;
  font-size: 1rem;
  cursor: pointer;
  margin-top: 10px;
  box-shadow: 0 4px 15px rgba(220, 38, 38, 0.3);
  transition:
    transform 0.2s,
    box-shadow 0.2s;
}

.action-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(220, 38, 38, 0.5);
}

.action-btn:active {
  transform: translateY(0);
}

/* Result Cards */
.result-card {
  margin-top: 25px;
  background: var(--card-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: 20px;
  text-align: center;
  box-shadow: var(--shadow-card);
  animation: slideUp 0.4s ease;
}

.result-card.hidden {
  display: none;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.big-number {
  font-size: 3rem;
  font-weight: 800;
  color: var(--primary-color);
  font-family: var(--font-display);
  margin-top: 10px;
  text-shadow: 0 0 20px rgba(220, 38, 38, 0.2);
}

.unit-display {
  font-size: 1rem;
  color: var(--text-muted);
  font-weight: 400;
}

/* Tables */
.table-responsive {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin-top: 10px;
}

.table-responsive::-webkit-scrollbar {
  height: 6px;
}

.table-responsive::-webkit-scrollbar-thumb {
  background: rgba(220, 38, 38, 0.4);
  border-radius: 4px;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 500px;
  /* Ensures table doesn't collapse too small */
}

.data-table th {
  text-align: left;
  color: var(--primary-color);
  padding: 10px;
  border-bottom: 1px solid var(--card-border);
  font-weight: 600;
  white-space: nowrap;
}

.data-table td {
  padding: 12px 10px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  font-variant-numeric: tabular-nums;
  text-align: left;
}

.data-table tr:last-child td {
  border-bottom: none;
}

/* RIR Results */
.rir-results {
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.rir-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.03);
}

.rir-item.highlight {
  background: rgba(220, 38, 38, 0.1);
  border: 1px solid rgba(220, 38, 38, 0.3);
}

.rir-item .value {
  font-weight: 700;
  font-size: 1.2rem;
}

.divider {
  height: 1px;
  background: var(--card-border);
  margin: 20px 0;
}

h4 {
  margin-bottom: 15px;
  color: var(--text-main);
}

/* Guide Section */
.guide-block {
  padding: 5px 0;
}

.guide-block h4 {
  margin-bottom: 8px;
  color: var(--primary-color);
  font-family: var(--font-display);
  font-size: 1.1rem;
}

.guide-block p {
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.5;
}

.main-footer {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.8rem;
  margin-top: 20px;
}

/* Responsive */
@media (max-width: 768px) {
  .main-header {
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 15px;
  }

  .settings-bar {
    width: 100%;
    justify-content: center;
    flex-wrap: wrap;
    gap: 10px;
  }

  .unit-btn,
  .lang-select,
  .legacy-btn,
  .guide-btn {
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .main-nav {
    justify-content: flex-start;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    /* Firefox */
  }

  .main-nav::-webkit-scrollbar {
    display: none;
    /* Chrome, Safari */
  }

  .nav-btn {
    flex: 0 0 auto;
  }
}

@media (max-width: 480px) {
  body {
    padding: 12px;
    padding-top: calc(12px + env(safe-area-inset-top));
  }

  .big-number {
    font-size: 2.2rem;
  }

  .row {
    flex-direction: column;
    gap: 12px;
  }

  .input-group {
    margin-bottom: 12px;
  }

  input,
  select,
  .action-btn {
    min-height: 48px;
    /* larger touch targets */
  }
}