:root {
  /* Colors */
  --primary: #1a365d;
  --primary-dark: #0f1419;
  --primary-light: #2d3748;
  --accent: #e53e3e;
  --accent-hover: #c53030;
  --text-primary: #1a202c;
  --text-secondary: #4a5568;
  --text-light: #718096;
  --bg-primary: #ffffff;
  --bg-secondary: #f7fafc;
  --bg-tertiary: #edf2f7;
  --border: #e2e8f0;
  --shadow: rgba(26, 32, 44, 0.1);
  --shadow-hover: rgba(26, 32, 44, 0.15);

  /* Typography */
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

  /* Spacing */
  --space-xs: clamp(0.5rem, 1vw, 0.75rem);
  --space-sm: clamp(0.75rem, 2vw, 1rem);
  --space-md: clamp(1rem, 3vw, 1.5rem);
  --space-lg: clamp(1.5rem, 4vw, 2rem);
  --space-xl: clamp(2rem, 5vw, 3rem);
  --space-2xl: clamp(3rem, 6vw, 4rem);
  --space-3xl: clamp(4rem, 8vw, 6rem);

  /* Layout */
  --container-max: 1200px;
  --header-height: 80px;
  --border-radius: 8px;
  --border-radius-lg: 12px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* ========================================
   RESET & BASE STYLES
   ======================================== */

*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  margin: 0;
  font-family: var(--font-primary);
  font-size: clamp(0.875rem, 2vw, 1rem);
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  line-height: 1.2;
  margin: 0 0 var(--space-md) 0;
  color: var(--text-primary);
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.5rem, 4vw, 2.5rem); }
h3 { font-size: clamp(1.25rem, 3vw, 2rem); }
h4 { font-size: clamp(1.125rem, 2.5vw, 1.5rem); }
h5 { font-size: clamp(1rem, 2vw, 1.25rem); }

p {
  margin: 0 0 var(--space-md) 0;
}

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

a:hover {
  color: var(--accent);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

button {
  font-family: inherit;
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
}

input, textarea, select {
  font-family: inherit;
  font-size: inherit;
}

/* ========================================
   UTILITY CLASSES
   ======================================== */

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-md);
}

.grid {
  display: grid;
  gap: var(--space-lg);
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.grid-4 {
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}

.flex {
  display: flex;
  gap: var(--space-md);
}

.flex-column {
  flex-direction: column;
}

.flex-center {
  align-items: center;
  justify-content: center;
}

.flex-between {
  justify-content: space-between;
  align-items: center;
}

.flex-wrap {
  flex-wrap: wrap;
}

.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mb-0 { margin-bottom: 0; }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

.mt-0 { margin-top: 0; }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }

.hidden { display: none !important; }
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ========================================
   HEADER
   ======================================== */

.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background-color: var(--bg-primary);
  z-index: 1000;
  transition: all var(--transition-normal);
  border-bottom: 1px solid var(--border);
}

.header.scrolled {
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  box-shadow: 0 2px 10px var(--shadow);
}

.header__container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: clamp(1.25rem, 3vw, 1.5rem);
  font-weight: 700;
  color: var(--primary);
  text-transform: lowercase;
}

.nav {
  display: flex;
  gap: var(--space-xl);
  align-items: center;
}

.nav__link {
  position: relative;
  padding: var(--space-sm) 0;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.nav__link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--accent);
  transition: width var(--transition-normal);
}

.nav__link:hover::after,
.nav__link.active::after {
  width: 100%;
}

.nav__link:hover,
.nav__link.active {
  color: var(--primary);
}

.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: var(--space-sm);
  background: none;
  border: none;
  cursor: pointer;
}

.mobile-menu-toggle span {
  width: 24px;
  height: 2px;
  background-color: var(--primary);
  transition: all var(--transition-fast);
  transform-origin: center;
}

.mobile-menu-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(6px, 6px);
}

.mobile-menu-toggle.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(6px, -6px);
}

/* ========================================
   MOBILE MENU
   ======================================== */

.mobile-menu {
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--bg-primary);
  transform: translateX(100%);
  transition: transform var(--transition-normal);
  z-index: 999;
  padding: var(--space-xl);
  overflow-y: auto;
}

.mobile-menu.active {
  transform: translateX(0);
}

.mobile-menu__nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.mobile-menu__link {
  padding: var(--space-md);
  font-size: 1.125rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--border-radius);
  transition: all var(--transition-fast);
  text-align: center;
}

.mobile-menu__link:hover,
.mobile-menu__link.active {
  background-color: var(--bg-secondary);
  color: var(--primary);
}

.mobile-menu-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.5);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
  z-index: 998;
}

.mobile-menu-overlay.active {
  opacity: 1;
  visibility: visible;
}

body.menu-open {
  overflow: hidden;
}

/* ========================================
   MAIN CONTENT
   ======================================== */

.main {
  margin-top: var(--header-height);
}

.section {
  padding: var(--space-3xl) 0;
}

.section--hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
  padding: var(--space-3xl) 0 var(--space-2xl) 0;
  min-height: calc(100vh - var(--header-height));
  display: flex;
  align-items: center;
}

.section--gray {
  background-color: var(--bg-secondary);
}

.section--dark {
  background-color: var(--primary);
  color: white;
}

/* ========================================
   HERO SECTION
   ======================================== */

.hero {
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
}

.hero__title {
  margin-bottom: var(--space-lg);
  font-weight: 700;
}

.hero__subtitle {
  font-size: clamp(1rem, 3vw, 1.25rem);
  color: var(--text-secondary);
  margin-bottom: var(--space-xl);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero__buttons {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  flex-wrap: wrap;
}

/* ========================================
   BUTTONS
   ======================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-md) var(--space-xl);
  border-radius: var(--border-radius);
  font-weight: 600;
  font-size: 1rem;
  text-decoration: none;
  transition: all var(--transition-fast);
  min-height: 48px;
  white-space: nowrap;
}

.btn--primary {
  background-color: var(--primary);
  color: white;
  border: 2px solid var(--primary);
}

.btn--primary:hover {
  background-color: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--shadow);
}

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

.btn--secondary:hover {
  background-color: var(--primary);
  color: white;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--shadow);
}

.btn--accent {
  background-color: var(--accent);
  color: white;
  border: 2px solid var(--accent);
}

.btn--accent:hover {
  background-color: var(--accent-hover);
  border-color: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--shadow);
}

.btn--small {
  padding: var(--space-sm) var(--space-md);
  font-size: 0.875rem;
}

.btn--block {
  width: 100%;
}

/* ========================================
   CARDS
   ======================================== */

.card {
  background-color: var(--bg-primary);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  box-shadow: 0 2px 10px var(--shadow);
  transition: all var(--transition-normal);
  border: 1px solid var(--border);
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px var(--shadow-hover);
}

.card__title {
  margin-bottom: var(--space-md);
  color: var(--primary);
}

.card__text {
  color: var(--text-secondary);
  margin-bottom: var(--space-lg);
}

.service-card {
  text-align: center;
}

.service-card__icon {
  width: 64px;
  height: 64px;
  margin: 0 auto var(--space-md);
  background-color: var(--accent);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.5rem;
  font-weight: bold;
}

.review-card {
  position: relative;
}

.review-card__rating {
  color: #fbbf24;
  margin-bottom: var(--space-sm);
}

.review-card__text {
  font-style: italic;
  margin-bottom: var(--space-md);
}

.review-card__author {
  font-weight: 600;
  color: var(--primary);
}

/* ========================================
   FORMS
   ======================================== */

.form {
  max-width: 500px;
  margin: 0 auto;
}

.form-group {
  margin-bottom: var(--space-lg);
}

.form-label {
  display: block;
  margin-bottom: var(--space-sm);
  font-weight: 500;
  color: var(--text-primary);
}

.form-input,
.form-textarea {
  width: 100%;
  padding: var(--space-md);
  border: 2px solid var(--border);
  border-radius: var(--border-radius);
  font-size: 1rem;
  transition: border-color var(--transition-fast);
  background-color: var(--bg-primary);
}

.form-input:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(26, 54, 93, 0.1);
}

.form-textarea {
  resize: vertical;
  min-height: 120px;
}

.form-error {
  color: var(--accent);
  font-size: 0.875rem;
  margin-top: var(--space-xs);
  display: none;
}

.form-error.show {
  display: block;
}

/* ========================================
   TOAST NOTIFICATIONS
   ======================================== */

.toast {
  position: fixed;
  top: calc(var(--header-height) + var(--space-md));
  right: var(--space-md);
  background-color: var(--bg-primary);
  border-radius: var(--border-radius);
  padding: var(--space-md);
  box-shadow: 0 4px 20px var(--shadow);
  border: 1px solid var(--border);
  transform: translateX(400px);
  opacity: 0;
  transition: all var(--transition-normal);
  z-index: 1001;
  max-width: 300px;
}

.toast.show {
  transform: translateX(0);
  opacity: 1;
}

.toast--success {
  border-color: #48bb78;
}

.toast--error {
  border-color: var(--accent);
}

/* ========================================
   FOOTER
   ======================================== */

.footer {
  background-color: var(--primary);
  color: white;
  padding: var(--space-3xl) 0 var(--space-xl) 0;
}

.footer__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--space-xl);
}

.footer__section h4 {
  color: white;
  margin-bottom: var(--space-md);
}

.footer__section p,
.footer__section a {
  color: rgba(255, 255, 255, 0.8);
  margin-bottom: var(--space-sm);
}

.footer__section a:hover {
  color: white;
}

.footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.footer__bottom {
  margin-top: var(--space-2xl);
  padding-top: var(--space-xl);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  text-align: center;
  color: rgba(255, 255, 255, 0.6);
}

/* ========================================
   ANIMATIONS
   ======================================== */

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: all var(--transition-slow);
}

.fade-in.animate {
  opacity: 1;
  transform: translateY(0);
}

.slide-in-left {
  opacity: 0;
  transform: translateX(-30px);
  transition: all var(--transition-slow);
}

.slide-in-left.animate {
  opacity: 1;
  transform: translateX(0);
}

.slide-in-right {
  opacity: 0;
  transform: translateX(30px);
  transition: all var(--transition-slow);
}

.slide-in-right.animate {
  opacity: 1;
  transform: translateX(0);
}

.scale-in {
  opacity: 0;
  transform: scale(0.9);
  transition: all var(--transition-slow);
}

.scale-in.animate {
  opacity: 1;
  transform: scale(1);
}

/* ========================================
   PRICING TABLES
   ======================================== */

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
  margin: var(--space-xl) 0;
}

.pricing-card {
  background-color: var(--bg-primary);
  border: 2px solid var(--border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  text-align: center;
  transition: all var(--transition-normal);
}

.pricing-card--featured {
  border-color: var(--primary);
  position: relative;
}

.pricing-card--featured::before {
  content: 'Προτεινόμενο';
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  background-color: var(--primary);
  color: white;
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--border-radius);
  font-size: 0.875rem;
  font-weight: 600;
}

.pricing-card__price {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 700;
  color: var(--primary);
  margin: var(--space-md) 0;
}

.pricing-card__period {
  font-size: 0.875rem;
  color: var(--text-light);
}

.pricing-card__features {
  list-style: none;
  padding: 0;
  margin: var(--space-lg) 0;
}

.pricing-card__features li {
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border);
}

.pricing-card__features li:last-child {
  border-bottom: none;
}

/* ========================================
   RESPONSIVE DESIGN
   ======================================== */

@media (max-width: 768px) {
  :root {
    --space-xs: 0.5rem;
    --space-sm: 0.75rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 2.5rem;
    --space-3xl: 3rem;
  }

  .header__container {
    padding: 0 var(--space-md);
  }

  .mobile-menu-toggle {
    display: flex;
  }

  .nav {
    display: none;
  }

  .hero__buttons {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    width: 100%;
    max-width: 280px;
  }

  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }

  .flex {
    flex-direction: column;
  }

  .flex-between {
    flex-direction: column;
    gap: var(--space-sm);
  }

  .footer__grid {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }

  .pricing-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-sm);
  }

  .section {
    padding: var(--space-2xl) 0;
  }

  .section--hero {
    padding: var(--space-2xl) 0 var(--space-xl) 0;
  }

  .card {
    padding: var(--space-lg);
  }

  .footer {
    padding: var(--space-2xl) 0 var(--space-lg) 0;
  }
}

/* ========================================
   ACCESSIBILITY
   ======================================== */

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* Focus styles for keyboard navigation */
.btn:focus,
.form-input:focus,
.form-textarea:focus,
.nav__link:focus,
.mobile-menu__link:focus {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --border: #000000;
    --text-secondary: #000000;
  }
}