:root {
  /* Light Mode Variables */
  --bg-color: #ffffff;
  --text-color: #1f2937;
  --secondary-text: #4b5563;
  --header-bg: rgba(255, 255, 255, 0.9);
  --glass-bg: rgba(255, 255, 255, 0.6);
  --glass-border: rgba(255, 255, 255, 0.3);
  --card-bg: #f3f4f6;
  --input-bg: #ffffff;
  --input-border: #d1d5db;
  
  /* Shared Theme Settings */
  --primary-red: #ef4444;       /* Hot */
  --primary-orange: #f97316;     /* Warm */
  --primary-blue: #0ea5e9;       /* Cool */
  --primary-teal: #14b8a6;       /* Cold */
  
  --gradient-hot: linear-gradient(135deg, var(--primary-red), var(--primary-orange));
  --gradient-cool: linear-gradient(135deg, var(--primary-blue), var(--primary-teal));
  --gradient-transition: linear-gradient(135deg, #ef4444 0%, #a855f7 50%, #0ea5e9 100%);
  
  --btn-shadow: 0 4px 14px 0 rgba(239, 68, 68, 0.39);
  --box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --border-radius: 12px;
  --transition: all 0.3s ease;
}

[data-theme="dark"] {
  --bg-color: #0f172a;
  --text-color: #f8fafc;
  --secondary-text: #cbd5e1;
  --header-bg: rgba(15, 23, 42, 0.9);
  --glass-bg: rgba(30, 41, 59, 0.7);
  --glass-border: rgba(255, 255, 255, 0.05);
  --card-bg: #1e293b;
  --input-bg: #334155;
  --input-border: #475569;
}

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

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color 0.4s ease, color 0.4s ease;
  line-height: 1.6;
  scroll-behavior: smooth;
  overflow-x: hidden;
}

/* Glassmorphism utility */
.glass {
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  box-shadow: var(--box-shadow);
}

/* Typography */
h1, h2, h3, h4 {
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 1rem;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; }
h3 { font-size: 1.5rem; }
p { margin-bottom: 1rem; color: var(--secondary-text); }

.text-gradient {
  background: var(--gradient-transition);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Layout */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Header & Navbar */
.navbar {
  position: fixed;
  top: 0;
  width: 100%;
  z-index: 100;
  background: var(--header-bg);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--glass-border);
  transition: var(--transition);
}

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

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-color);
  font-weight: 500;
  transition: var(--transition);
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary-red);
  transition: var(--transition);
}

.nav-links a:hover::after {
  width: 100%;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.theme-toggle {
  background: none;
  border: none;
  color: var(--text-color);
  font-size: 1.25rem;
  cursor: pointer;
  padding: 8px;
  border-radius: 50%;
  transition: var(--transition);
}

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

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text-color);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 28px;
  border-radius: var(--border-radius);
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  border: none;
  transition: var(--transition);
  gap: 8px;
}

.btn-primary {
  background: var(--gradient-hot);
  color: white;
  box-shadow: var(--btn-shadow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px 0 rgba(239, 68, 68, 0.5);
  background: var(--gradient-cool);
}

.btn-outline {
  background: transparent;
  color: var(--text-color);
  border: 2px solid var(--primary-red);
}

.btn-outline:hover {
  background: var(--primary-red);
  color: white;
}

/* Hero Section */
.hero {
  padding: 140px 0 80px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 80vw;
  height: 80vw;
  background: radial-gradient(circle, rgba(239,68,68,0.1) 0%, rgba(14,165,233,0.05) 50%, rgba(0,0,0,0) 70%);
  z-index: -1;
  pointer-events: none;
}

.hero p {
  font-size: 1.25rem;
  max-width: 600px;
  margin: 0 auto 2rem;
}

.hero-btns {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Affiliate Banner */
.affiliate-section {
  padding: 60px 0;
}

.affiliate-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
}

.affiliate-image {
  width: 100%;
  aspect-ratio: 1/1;
  background: var(--card-bg);
  border-radius: var(--border-radius);
  overflow: hidden;
  transition: var(--transition);
  box-shadow: var(--box-shadow);
}

.affiliate-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.affiliate-image:hover {
  transform: scale(1.02);
}

.affiliate-image:hover img {
  transform: scale(1.05);
}

/* Calculator Section */
.calculator-section {
  padding: 80px 0;
  position: relative;
}

.calculator-wrapper {
  max-width: 800px;
  margin: 0 auto;
  border-radius: 20px;
  padding: 40px;
}

.calc-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
}

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

.input-group label {
  display: block;
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 8px;
  color: var(--secondary-text);
}

.input-group input {
  width: 100%;
  padding: 16px;
  border-radius: 8px;
  border: 2px solid var(--input-border);
  background: var(--input-bg);
  color: var(--text-color);
  font-size: 1.1rem;
  font-family: inherit;
  font-weight: 500;
  transition: var(--transition);
  box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.02);
}

.input-group input:focus {
  outline: none;
  border-color: var(--primary-blue);
  box-shadow: 0 0 0 4px rgba(14, 165, 233, 0.15);
  transform: translateY(-2px);
}

.calc-results {
  background: linear-gradient(145deg, #1e293b, #0f172a);
  color: white;
  border-radius: 16px;
  padding: 2.5rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 1.5rem;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  position: relative;
  overflow: hidden;
}

.calc-results::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--gradient-transition);
}

[data-theme="dark"] .calc-results {
  background: linear-gradient(145deg, #334155, #1e293b);
}

.result-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 1rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.result-item:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.result-item span:first-child {
  color: #cbd5e1;
  font-weight: 500;
  font-size: 1.1rem;
}

.result-item.total {
  margin-top: 1rem;
  padding-top: 1.5rem;
  border-top: 2px dashed rgba(255, 255, 255, 0.2);
  border-bottom: none;
}

.result-item.total span:first-child {
  font-size: 1.3rem;
  color: white;
  font-weight: 700;
}

.result-item.total .result-value {
  color: #38bdf8;
}

.result-item.total .result-value span {
  font-size: 2.5rem;
  font-weight: 900;
  letter-spacing: -1px;
}

.result-value {
  font-size: 1.2rem;
  font-weight: 600;
}

.result-value span {
  font-size: 1.5rem;
  font-weight: 800;
}

/* Article / SEO Section */
.seo-section {
  padding: 80px 0;
}

.seo-content {
  max-width: 800px;
  margin: 0 auto;
}

.seo-content h2, .seo-content h3 {
  margin-top: 2rem;
}

.seo-content ul {
  padding-left: 1.5rem;
  margin-bottom: 1.5rem;
  color: var(--secondary-text);
}

.seo-content li {
  margin-bottom: 0.5rem;
}

/* Forms */
.contact-form {
  max-width: 600px;
  margin: 0 auto;
  .input-group { margin-bottom: 1rem; }
  textarea {
    width: 100%;
    padding: 14px;
    border-radius: var(--border-radius);
    border: 1px solid var(--input-border);
    background: var(--input-bg);
    color: var(--text-color);
    font-size: 1rem;
    resize: vertical;
    min-height: 150px;
  }
}

/* General Content Pages */
.page-header {
  padding: 120px 0 60px;
  text-align: center;
  background: var(--card-bg);
  margin-bottom: 40px;
}

.content-wrapper {
  max-width: 800px;
  margin: 0 auto 80px;
}

/* Footer */
footer {
  background: var(--card-bg);
  padding: 60px 0 20px;
  border-top: 1px solid var(--glass-border);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2rem;
  margin-bottom: 40px;
}

.footer-col h4 {
  margin-bottom: 1rem;
}

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

.footer-col ul li {
  margin-bottom: 0.5rem;
}

.footer-col a {
  color: var(--secondary-text);
  text-decoration: none;
  transition: var(--transition);
}

.footer-col a:hover {
  color: var(--primary-red);
}

.footer-bottom {
  text-align: center;
  padding-top: 20px;
  border-top: 1px solid var(--input-border);
  color: var(--secondary-text);
  font-size: 0.875rem;
}

/* Utilities & Animations */
.animate-on-scroll {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.animate-on-scroll.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.text-center { text-align: center; }
.mb-2 { margin-bottom: 2rem; }
.mt-2 { margin-top: 2rem; }

/* Responsive Media Queries */
@media (max-width: 768px) {
  h1 { font-size: 2.5rem; }
  .calc-grid, .affiliate-grid {
    grid-template-columns: 1fr;
  }
  .nav-links {
    display: none; /* simple initial mobile nav approach */
    position: absolute;
    top: 70px;
    left: 0;
    width: 100%;
    background: var(--header-bg);
    flex-direction: column;
    padding: 20px;
    box-shadow: var(--box-shadow);
  }
  .nav-links.active {
    display: flex;
  }
  .hamburger {
    display: block;
  }
}