/* ===================================
   Modern Design System - CSS Variables
   =================================== */

:root {
  /* Color Palette */
  --color-primary-50: #eff6ff;
  --color-primary-100: #dbeafe;
  --color-primary-200: #bfdbfe;
  --color-primary-300: #93c5fd;
  --color-primary-400: #60a5fa;
  --color-primary-500: #3b82f6;
  --color-primary-600: #2563eb;
  --color-primary-700: #1d4ed8;
  --color-primary-800: #1e40af;
  --color-primary-900: #1e3a8a;

  /* Semantic Colors - Light Theme */
  --color-primary: var(--color-primary-600);
  --color-primary-hover: var(--color-primary-700);
  --color-primary-light: var(--color-primary-50);
  --color-secondary: #6b7280;
  --color-accent: #8b5cf6;

  /* Text Colors */
  --color-text-primary: #111827;
  --color-text-secondary: #6b7280;
  --color-text-tertiary: #9ca3af;
  --color-text-inverse: #ffffff;

  /* Background Colors */
  --color-background: #ffffff;
  --color-surface: #f9fafb;
  --color-surface-elevated: #ffffff;
  --color-overlay: rgba(0, 0, 0, 0.5);

  /* Border Colors */
  --color-border-light: #e5e7eb;
  --color-border: #d1d5db;
  --color-border-strong: #9ca3af;

  /* Status Colors */
  --color-success: #10b981;
  --color-success-light: #d1fae5;
  --color-warning: #f59e0b;
  --color-warning-light: #fef3c7;
  --color-error: #ef4444;
  --color-error-light: #fee2e2;
  --color-info: #3b82f6;
  --color-info-light: #dbeafe;

  /* Typography Scale */
  --font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
  --font-family-mono: 'SF Mono', Monaco, Inconsolata, 'Roboto Mono', source-code-pro, monospace;

  --font-size-xs: 0.75rem;    /* 12px */
  --font-size-sm: 0.875rem;   /* 14px */
  --font-size-base: 1rem;     /* 16px */
  --font-size-lg: 1.125rem;   /* 18px */
  --font-size-xl: 1.25rem;    /* 20px */
  --font-size-2xl: 1.5rem;    /* 24px */
  --font-size-3xl: 1.875rem;  /* 30px */
  --font-size-4xl: 2.25rem;   /* 36px */

  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.75;

  /* Spacing Scale */
  --space-0: 0;
  --space-1: 0.25rem;   /* 4px */
  --space-2: 0.5rem;    /* 8px */
  --space-3: 0.75rem;   /* 12px */
  --space-4: 1rem;      /* 16px */
  --space-5: 1.25rem;   /* 20px */
  --space-6: 1.5rem;    /* 24px */
  --space-8: 2rem;      /* 32px */
  --space-10: 2.5rem;   /* 40px */
  --space-12: 3rem;     /* 48px */
  --space-16: 4rem;     /* 64px */
  --space-20: 5rem;     /* 80px */

  /* Border Radius */
  --radius-none: 0;
  --radius-sm: 0.25rem;
  --radius-base: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-2xl: 1.5rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-base: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.06);

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 200ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 300ms cubic-bezier(0.4, 0, 0.2, 1);

  /* Z-Index Scale */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal-backdrop: 1040;
  --z-modal: 1050;
  --z-popover: 1060;
  --z-tooltip: 1070;
  --z-toast: 1080;

  /* Layout */
  --container-max-width: 1280px;
  --header-height: 4rem;
  --card-min-width: 320px;
}

/* Dark Theme */
@media (prefers-color-scheme: dark) {
  :root {
    /* Semantic Colors - Dark Theme */
    --color-primary: var(--color-primary-400);
    --color-primary-hover: var(--color-primary-300);
    --color-primary-light: var(--color-primary-900);
    --color-secondary: #9ca3af;
    --color-accent: #a78bfa;

    /* Text Colors - Dark Theme */
    --color-text-primary: #f9fafb;
    --color-text-secondary: #d1d5db;
    --color-text-tertiary: #9ca3af;

    /* Background Colors - Dark Theme */
    --color-background: #111827;
    --color-surface: #1f2937;
    --color-surface-elevated: #374151;
    --color-overlay: rgba(0, 0, 0, 0.7);

    /* Border Colors - Dark Theme */
    --color-border-light: #374151;
    --color-border: #4b5563;
    --color-border-strong: #6b7280;
  }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  :root {
    --transition-fast: 0ms;
    --transition-base: 0ms;
    --transition-slow: 0ms;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ===================================
   Base Styles & Reset
   =================================== */

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

html {
  line-height: var(--line-height-normal);
  -webkit-text-size-adjust: 100%;
  -moz-tab-size: 4;
  tab-size: 4;
  font-family: var(--font-family-base);
  font-feature-settings: normal;
  font-variation-settings: normal;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  background-color: var(--color-background);
  color: var(--color-text-primary);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  min-height: 100vh;
  text-rendering: optimizeSpeed;
}

/* Screen reader only content */
.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 */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

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

a:hover {
  color: var(--color-primary-hover);
  text-decoration: underline;
}

/* ===================================
   Layout Components
   =================================== */

.app-container {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--space-4);
}

@media (min-width: 640px) {
  .container {
    padding: 0 var(--space-6);
  }
}

@media (min-width: 1024px) {
  .container {
    padding: 0 var(--space-8);
  }
}

/* ===================================
   Header Component
   =================================== */

.app-header {
  background-color: var(--color-surface-elevated);
  border-bottom: 1px solid var(--color-border-light);
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  background-color: color-mix(in srgb, var(--color-surface-elevated) 95%, transparent);
}

.header-content {
  height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.brand-icon {
  font-size: var(--font-size-2xl);
  color: var(--color-primary);
  flex-shrink: 0;
}

.brand-text {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.brand-title {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text-primary);
  line-height: var(--line-height-tight);
  margin: 0;
}

.brand-subtitle {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-normal);
  margin: 0;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

/* ===================================
   Button Components
   =================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 500;
  line-height: var(--line-height-normal);
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  background: none;
  font-family: inherit;
  white-space: nowrap;
}

.btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

/* Button Variants */
.btn--primary {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
  border-color: var(--color-primary);
}

.btn--primary:hover:not(:disabled) {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  color: var(--color-text-inverse);
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: var(--shadow-lg);
}

.btn--secondary {
  background-color: var(--color-surface);
  color: var(--color-text-primary);
  border-color: var(--color-border);
}

.btn--secondary:hover:not(:disabled) {
  background-color: var(--color-surface-elevated);
  border-color: var(--color-border-strong);
  color: var(--color-text-primary);
  text-decoration: none;
}

.btn--icon {
  padding: var(--space-2);
  min-width: auto;
}

.btn--icon .btn__text {
  display: none;
}

@media (min-width: 768px) {
  .btn--icon .btn__text {
    display: inline;
  }
}

/* ===================================
   Main Content Area
   =================================== */

.main-content {
  flex: 1;
  padding: var(--space-6) 0;
}

/* ===================================
   Project Cards Grid
   =================================== */

.projects-section {
  width: 100%;
  opacity: 1;
  transition: opacity var(--transition-base);
}

.projects-section[hidden] {
  display: none;
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, var(--card-min-width)), 1fr));
  gap: 3rem var(--space-8);
  align-items: start;
}

.project-card {
  background-color: var(--color-surface-elevated);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin-bottom: 2rem;
  transition: all var(--transition-fast);
  position: relative;
  overflow: hidden;
}

.project-card:hover {
  border-color: var(--color-border);
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.project-card:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.project-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.project-title {
  flex: 1;
  min-width: 0;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.project-title-link {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-text-primary);
  line-height: var(--line-height-tight);
  word-break: break-word;
  flex: 1;
  min-width: 0;
}

.project-title-link:hover {
  color: var(--color-primary);
  text-decoration: underline;
}

.project-title-github {
  color: var(--color-text-secondary);
  font-size: var(--font-size-base);
  transition: color var(--transition-fast);
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
}

.project-title-github:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.project-stars {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  font-weight: 500;
  white-space: nowrap;
  flex-shrink: 0;
}

.project-stars i {
  color: #fbbf24;
}

.project-description {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
}

.project-description p {
  margin-bottom: var(--space-3);
}

.project-description p:last-child {
  margin-bottom: 0;
}

.project-description strong {
  color: var(--color-text-primary);
  font-weight: 600;
}

.project-description code {
  background-color: var(--color-surface);
  color: var(--color-error);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  font-family: var(--font-family-mono);
  font-size: 0.875em;
}

.project-description ul,
.project-description ol {
  margin-left: var(--space-4);
  margin-bottom: var(--space-3);
}

.project-description li {
  margin-bottom: var(--space-1);
}

/* ===================================
   Loading States
   =================================== */

.skeleton-section {
  width: 100%;
  opacity: 1;
  transition: opacity var(--transition-base);
}

.skeleton-section[hidden] {
  display: none;
}

.skeleton-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, var(--card-min-width)), 1fr));
  gap: 3rem var(--space-8);
}

.skeleton-card {
  background-color: var(--color-surface-elevated);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin-bottom: 2rem;
}

.skeleton-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.skeleton-avatar {
  width: 2.5rem;
  height: 2.5rem;
  background: linear-gradient(
    90deg,
    var(--color-border-light) 25%,
    var(--color-border) 50%,
    var(--color-border-light) 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-full);
  flex-shrink: 0;
}

.skeleton-info {
  flex: 1;
  min-width: 0;
}

.skeleton-title {
  height: 1.25rem;
  background: linear-gradient(
    90deg,
    var(--color-border-light) 25%,
    var(--color-border) 50%,
    var(--color-border-light) 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-2);
  width: 70%;
}

.skeleton-meta {
  height: 1rem;
  background: linear-gradient(
    90deg,
    var(--color-border-light) 25%,
    var(--color-border) 50%,
    var(--color-border-light) 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
  width: 40%;
}

.skeleton-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.skeleton-line {
  height: 1rem;
  background: linear-gradient(
    90deg,
    var(--color-border-light) 25%,
    var(--color-border) 50%,
    var(--color-border-light) 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
}

.skeleton-line.short {
  width: 60%;
}

@keyframes shimmer {
  0% {
    background-position: -200% 0;
  }
  100% {
    background-position: 200% 0;
  }
}

/* ===================================
   Error and Empty States
   =================================== */

.error-section,
.empty-section {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 50vh;
  text-align: center;
}

.error-section[hidden],
.empty-section[hidden] {
  display: none;
}

.error-content,
.empty-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
  max-width: 400px;
}

.error-icon,
.empty-icon {
  font-size: var(--font-size-4xl);
  color: var(--color-text-tertiary);
}

.error-title,
.empty-title {
  font-size: var(--font-size-2xl);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0;
}

.error-message,
.empty-message {
  color: var(--color-text-secondary);
  font-size: var(--font-size-base);
  line-height: var(--line-height-relaxed);
  margin: 0;
}

.error-actions {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
  justify-content: center;
}

/* ===================================
   Skip Link for Accessibility
   =================================== */

.skip-link {
  position: absolute;
  top: -40px;
  left: var(--space-4);
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
  padding: var(--space-2) var(--space-4);
  text-decoration: none;
  border-radius: var(--radius-md);
  z-index: var(--z-tooltip);
  font-weight: 500;
  transition: all var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
}

/* ===================================
   Toast Notifications
   =================================== */

.toast-container {
  position: fixed;
  top: var(--space-4);
  right: var(--space-4);
  z-index: var(--z-toast);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  pointer-events: none;
}

.toast {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  min-width: 300px;
  max-width: 500px;
  pointer-events: auto;
  animation: toast-slide-in 0.3s ease-out;
  transition: all var(--transition-base);
}

.toast--success {
  border-left: 4px solid var(--color-success);
  background-color: var(--color-success-light);
}

.toast--error {
  border-left: 4px solid var(--color-error);
  background-color: var(--color-error-light);
}

.toast--warning {
  border-left: 4px solid var(--color-warning);
  background-color: var(--color-warning-light);
}

.toast--info {
  border-left: 4px solid var(--color-info);
  background-color: var(--color-info-light);
}

.toast__icon {
  font-size: var(--font-size-lg);
  flex-shrink: 0;
}

.toast--success .toast__icon { color: var(--color-success); }
.toast--error .toast__icon { color: var(--color-error); }
.toast--warning .toast__icon { color: var(--color-warning); }
.toast--info .toast__icon { color: var(--color-info); }

.toast__content {
  flex: 1;
}

.toast__title {
  font-weight: 600;
  margin-bottom: var(--space-1);
  color: var(--color-text-primary);
}

.toast__message {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height-normal);
}

.toast__close {
  background: none;
  border: none;
  color: var(--color-text-tertiary);
  cursor: pointer;
  padding: var(--space-1);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.toast__close:hover {
  background-color: var(--color-surface);
  color: var(--color-text-primary);
}

.toast.hiding {
  animation: toast-slide-out 0.3s ease-in forwards;
}

@keyframes toast-slide-in {
  from {
    transform: translateX(100%);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

@keyframes toast-slide-out {
  from {
    transform: translateX(0);
    opacity: 1;
  }
  to {
    transform: translateX(100%);
    opacity: 0;
  }
}

/* ===================================
   NoScript Overlay
   =================================== */

.noscript-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--color-overlay);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: var(--z-modal);
  backdrop-filter: blur(4px);
}

.noscript-content {
  background-color: var(--color-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  max-width: 400px;
  text-align: center;
  box-shadow: var(--shadow-2xl);
}

.noscript-content i {
  font-size: var(--font-size-4xl);
  color: var(--color-error);
  margin-bottom: var(--space-4);
}

.noscript-content h2 {
  font-size: var(--font-size-2xl);
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
}

.noscript-content p {
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  margin-bottom: var(--space-2);
}

.noscript-content p:last-child {
  margin-bottom: 0;
}

/* ===================================
   Responsive Design
   =================================== */

@media (max-width: 640px) {
  .header-content {
    gap: var(--space-2);
  }

  .brand-text {
    display: none;
  }

  .main-content {
    padding: var(--space-4) 0;
  }

  .projects-grid,
  .skeleton-grid {
    gap: var(--space-4);
  }

  .project-card,
  .skeleton-card {
    padding: var(--space-4);
  }

  .project-header {
    align-items: flex-start;
    gap: var(--space-2);
  }

  .project-title {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-1);
  }

  .project-stars {
    align-self: flex-end;
  }

  .toast-container {
    top: var(--space-2);
    right: var(--space-2);
    left: var(--space-2);
  }

  .toast {
    min-width: auto;
    max-width: none;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-3);
  }

  .error-actions {
    flex-direction: column;
    width: 100%;
  }

  .error-actions .btn {
    width: 100%;
    justify-content: center;
  }
}

/* ===================================
   Print Styles
   =================================== */

@media print {
  .app-header,
  .toast-container,
  .skeleton-section,
  .error-section,
  .empty-section {
    display: none !important;
  }

  .projects-grid {
    grid-template-columns: 1fr;
    gap: var(--space-4);
  }

  .project-card {
    break-inside: avoid;
    box-shadow: none;
    border: 1px solid var(--color-border);
  }
}