@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --accent-primary: #4f46e5;
  --accent-hover: #4338ca;
  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --radius: 12px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent-primary: #6366f1;
  --accent-hover: #818cf8;
  --border-color: #334155;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.5);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.6), 0 2px 4px -2px rgb(0 0 0 / 0.6);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.6), 0 4px 6px -4px rgb(0 0 0 / 0.6);
}

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

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color 0.3s, color 0.3s;
  overflow-x: hidden;
}

a {
  text-decoration: none;
  color: var(--accent-primary);
  transition: var(--transition);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Header */
.header {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  transition: var(--transition);
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.logo span {
  color: var(--accent-primary);
}

.nav-links {
  display: flex;
  gap: 2rem;
  align-items: center;
}

.nav-links a {
  color: var(--text-secondary);
  font-weight: 500;
}

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

.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-primary);
  font-size: 1.25rem;
  padding: 0.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  transition: var(--transition);
}

.theme-toggle:hover {
  background-color: var(--bg-primary);
}

/* Hero Section */
.hero {
  padding: 6rem 0 4rem;
  text-align: center;
}

.hero .badge {
  display: inline-block;
  padding: 0.25rem 1rem;
  background-color: rgba(79, 70, 229, 0.1);
  color: var(--accent-primary);
  border-radius: 9999px;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
}

[data-theme="dark"] .hero .badge {
  background-color: rgba(99, 102, 241, 0.2);
}

.hero h1 {
  font-size: 3.5rem;
  font-weight: 800;
  margin-bottom: 1.5rem;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

.hero p {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 650px;
  margin: 0 auto 2.5rem;
}

/* Grid & Cards */
.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 2rem;
  padding: 2rem 0 6rem;
}

.tool-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  box-shadow: var(--shadow-sm);
  position: relative;
  overflow: hidden;
}

.tool-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: var(--accent-primary);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s ease;
}

.tool-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
  border-color: var(--border-color);
}

.tool-card:hover::before {
  transform: scaleX(1);
}

.card-header {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.tool-icon {
  width: 48px;
  height: 48px;
  background-color: rgba(79, 70, 229, 0.1);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: var(--accent-primary);
}

[data-theme="dark"] .tool-icon {
  background-color: rgba(99, 102, 241, 0.2);
}

.tool-card h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
}

.tool-card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  flex-grow: 1;
}

.tool-card .link-text {
  margin-top: auto;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

/* Sections */
.section-title {
  text-align: center;
  font-size: 2.25rem;
  font-weight: 800;
  margin-bottom: 3rem;
  color: var(--text-primary);
}

/* FAQ */
.faq-section {
  padding: 4rem 0 6rem;
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  margin-bottom: 1rem;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.faq-question {
  padding: 1.5rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 600;
  font-size: 1.1rem;
}

.faq-answer {
  padding: 0 1.5rem;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
  color: var(--text-secondary);
}

.faq-item.active .faq-answer {
  padding: 0 1.5rem 1.5rem;
  max-height: 500px;
}

/* Tool Pages */
.tool-header {
  background-color: var(--bg-secondary);
  padding: 4rem 0 3rem;
  text-align: center;
  border-bottom: 1px solid var(--border-color);
}

.tool-header h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 1rem;
}

.tool-header p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  max-width: 700px;
  margin: 0 auto;
}

.tool-layout {
  display: grid;
  grid-template-columns: 1fr 1.2fr;
  gap: 3rem;
  padding: 4rem 0;
}

@media (max-width: 900px) {
  .tool-layout {
    grid-template-columns: 1fr;
  }
}

.calculator-panel {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
}

.results-panel {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow-md);
  position: sticky;
  top: 100px;
  height: max-content;
}

.input-group {
  margin-bottom: 1.5rem;
}

.input-group label {
  display: block;
  font-weight: 600;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.input-prefix {
  position: absolute;
  left: 1rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.input-suffix {
  position: absolute;
  right: 1rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.input-group input,
.input-group select,
.input-group textarea {
  width: 100%;
  padding: 0.875rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 1rem;
  transition: var(--transition);
}

.input-wrapper.has-prefix input { padding-left: 2.25rem; }
.input-wrapper.has-suffix input { padding-right: 2.25rem; }

.input-group input:focus,
.input-group select:focus,
.input-group textarea:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

[data-theme="dark"] .input-group input:focus {
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.result-card h3 {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

.result-value {
  font-size: 3rem;
  font-weight: 800;
  color: var(--accent-primary);
  margin-bottom: 1rem;
  line-height: 1;
}

.result-value.negative {
  color: #ef4444;
}

.result-value.positive {
  color: #10b981;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.875rem 1.5rem;
  border-radius: 8px;
  font-weight: 600;
  transition: var(--transition);
  cursor: pointer;
  border: none;
  font-size: 1rem;
  width: 100%;
}

.btn-primary {
  background-color: var(--accent-primary);
  color: #ffffff;
}

.btn-primary:hover {
  background-color: var(--accent-hover);
  color: #ffffff;
}

.tool-article {
  padding: 3rem 0;
  max-width: 800px;
  margin: 0 auto;
}

.tool-article h2, .tool-article h3 {
  margin: 2rem 0 1rem;
}

.tool-article p {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

/* Footer */
.footer {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 4rem 0 2rem;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 3rem;
  margin-bottom: 3rem;
}

@media (max-width: 768px) {
  .footer-grid {
    grid-template-columns: 1fr;
  }
}

.footer-col h4 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  color: var(--text-primary);
}

.footer-col p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.footer-col ul {
  list-style: none;
}

.footer-col ul li {
  margin-bottom: 0.75rem;
}

.footer-col ul li a {
  color: var(--text-secondary);
  transition: var(--transition);
}

.footer-col ul li a:hover {
  color: var(--accent-primary);
}

.footer-bottom {
  text-align: center;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.9rem;
}