@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
  /* Nord Color Palette */
  --nord0: #2E3440; /* Polar Night - Darkest */
  --nord1: #3B4252;
  --nord2: #434C5E;
  --nord3: #4C566A; /* Polar Night - Lightest */
  
  --nord4: #D8DEE9; /* Snow Storm - Darkest */
  --nord5: #E5E9F0;
  --nord6: #ECEFF4; /* Snow Storm - Lightest */
  
  --nord7: #8FBCBB; /* Frost - Greenish */
  --nord8: #88C0D0; /* Frost - Cyan */
  --nord9: #81A1C1; /* Frost - Blue */
  --nord10: #5E81AC; /* Frost - Dark Blue */
  
  --nord11: #BF616A; /* Aurora - Red */
  --nord12: #D08770; /* Aurora - Orange */
  --nord13: #EBCB8B; /* Aurora - Yellow */
  --nord14: #A3BE8C; /* Aurora - Green */
  --nord15: #B48EAD; /* Aurora - Purple */

  /* Theme variables */
  --bg-color: var(--nord0);
  --text-primary: var(--nord6);
  --text-secondary: var(--nord4);
  --accent-color: var(--nord8);
  --glass-bg: rgba(59, 66, 82, 0.4);
  --glass-border: rgba(216, 222, 233, 0.1);
  --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.3);
}

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

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
}

/* Animated Gradient Background for Glassmorphism effect */
body::before {
  content: '';
  position: fixed;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at 50% 50%, rgba(136, 192, 208, 0.15) 0%, transparent 40%),
              radial-gradient(circle at 20% 80%, rgba(180, 142, 173, 0.15) 0%, transparent 40%),
              radial-gradient(circle at 80% 20%, rgba(94, 129, 172, 0.15) 0%, transparent 40%);
  z-index: -1;
  animation: bgPulse 20s ease-in-out infinite alternate;
}

@keyframes bgPulse {
  0% { transform: rotate(0deg) scale(1); }
  100% { transform: rotate(15deg) scale(1.1); }
}

/* Layout */
.app-container {
  display: flex;
  min-height: 100vh;
  padding: 1.5rem;
  gap: 1.5rem;
  max-width: 1400px;
  margin: 0 auto;
}

/* Sidebar Menu */
.sidebar {
  width: 280px;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
}

/* Glassmorphism Panel */
.glass-panel {
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: 20px;
  box-shadow: var(--glass-shadow);
  padding: 1.5rem;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--glass-border);
}

.logo-container {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.mobile-menu-btn {
  display: none;
  background: transparent;
  border: none;
  color: var(--nord6);
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.5rem;
  border-radius: 8px;
  transition: background 0.3s ease;
}

.mobile-menu-btn:hover {
  background: rgba(255, 255, 255, 0.1);
}

.logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--nord8), var(--nord10));
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 1.2rem;
  color: var(--nord0);
  box-shadow: 0 4px 12px rgba(136, 192, 208, 0.3);
}

.logo-text {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  background: linear-gradient(to right, var(--nord6), var(--nord8));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.menu-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.menu-item a {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  padding: 0.8rem 1rem;
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: 12px;
  transition: all 0.3s ease;
  font-weight: 500;
}

.menu-item a:hover {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
  transform: translateX(4px);
}

.menu-item.active a {
  background: rgba(136, 192, 208, 0.15);
  color: var(--accent-color);
  border-left: 3px solid var(--accent-color);
  border-radius: 0 12px 12px 0;
}

.menu-item i {
  font-size: 1.1rem;
  width: 24px;
  text-align: center;
}

/* Main Content */
.main-content {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  min-width: 0;
}

.content-header {
  padding: 2rem;
}

.content-header h1 {
  font-size: 2.2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--nord6);
}

.content-header p.subtitle {
  color: var(--nord9);
  font-size: 1.1rem;
}

.content-body {
  padding: 2rem;
  flex-grow: 1;
}

/* Typography & Markdown-like styling */
h2 {
  color: var(--nord8);
  font-size: 1.6rem;
  margin-top: 2rem;
  margin-bottom: 1rem;
  border-bottom: 1px solid var(--glass-border);
  padding-bottom: 0.5rem;
}

h3 {
  color: var(--nord7);
  font-size: 1.3rem;
  margin-top: 1.5rem;
  margin-bottom: 0.8rem;
}

p {
  margin-bottom: 1rem;
}

.math-block {
  background: rgba(0, 0, 0, 0.2);
  padding: 1.5rem;
  border-radius: 12px;
  margin: 1.5rem 0;
  overflow-x: auto;
  border: 1px solid rgba(136, 192, 208, 0.2);
  text-align: center;
}

/* MathJax specific overrides to ensure it's white */
.MathJax {
  color: var(--nord6) !important;
}

.example-box {
  background: rgba(163, 190, 140, 0.1);
  border-left: 4px solid var(--nord14);
  padding: 1.2rem;
  border-radius: 0 12px 12px 0;
  margin: 1.5rem 0;
}

.example-box h4 {
  color: var(--nord14);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.note-box {
  background: rgba(235, 203, 139, 0.1);
  border-left: 4px solid var(--nord13);
  padding: 1.2rem;
  border-radius: 0 12px 12px 0;
  margin: 1.5rem 0;
}

.note-box h4 {
  color: var(--nord13);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

ul, ol {
  margin-left: 1.5rem;
  margin-bottom: 1rem;
}

li {
  margin-bottom: 0.5rem;
}

strong {
  color: var(--nord6);
  font-weight: 600;
}

code {
  font-family: 'JetBrains Mono', monospace;
  background: rgba(0, 0, 0, 0.3);
  padding: 0.2rem 0.4rem;
  border-radius: 4px;
  color: var(--nord13);
  font-size: 0.9em;
}

/* Responsive */
@media (max-width: 900px) {
  .app-container {
    flex-direction: column;
    padding: 1rem;
  }
  
  .sidebar {
    width: 100%;
  }

  .sidebar-header {
    margin-bottom: 1rem;
  }

  .mobile-menu-btn {
    display: block;
  }
  
  .menu-list {
    display: none; /* Ẩn menu mặc định trên mobile */
    flex-direction: column;
    width: 100%;
    margin-bottom: 1rem;
  }

  .menu-list.show {
    display: flex;
    animation: fadeIn 0.3s ease;
  }

  .sidebar-footer {
    display: none;
  }

  .sidebar-footer.show {
    display: block;
  }
  
  .menu-item {
    flex: 1 1 100%; 
  }
}

@media (max-width: 600px) {
  .app-container {
    padding: 0.5rem;
  }
  
  .glass-panel {
    padding: 1rem;
    border-radius: 12px;
  }

  .content-header h1 {
    font-size: 1.6rem;
  }

  h2 {
    font-size: 1.3rem;
  }

  .math-block {
    font-size: 0.9rem;
    padding: 1rem 0.5rem;
  }
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}