:root {
  --bg-color: #0f172a;
  --card-bg: #1e293b;
  --accent-primary: #3b82f6;
  --accent-secondary: #8b5cf6;
  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  --border-color: #334155;
  --glass-bg: rgba(30, 41, 59, 0.7);
  --success: #10b981;
  --warning: #f59e0b;
}

* {
  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-main);
  line-height: 1.6;
  overflow-x: hidden;
}

.app-container {
  display: flex;
  height: 100vh;
  width: 100vw;
}

/* Sidebar */
.sidebar {
  width: 320px;
  background: var(--card-bg);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  padding: 2rem;
  transition: transform 0.3s ease;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  background: linear-gradient(to right, var(--accent-primary), var(--accent-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 2rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

/* Chat Main Area */
.chat-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  position: relative;
  background: radial-gradient(circle at top right, rgba(59, 130, 246, 0.05), transparent),
              radial-gradient(circle at bottom left, rgba(139, 92, 246, 0.05), transparent);
}

.chat-header {
  padding: 1.5rem 2rem;
  border-bottom: 1px solid var(--border-color);
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 10;
}

.messages-container {
  flex: 1;
  overflow-y: auto;
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.message {
  max-width: 80%;
  padding: 1rem 1.5rem;
  border-radius: 1rem;
  animation: slideUp 0.3s ease-out;
}

.message.user {
  align-self: flex-end;
  background: var(--accent-primary);
  color: white;
  border-bottom-right-radius: 0.2rem;
}

.message.assistant {
  align-self: flex-start;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-bottom-left-radius: 0.2rem;
}

.input-area {
  padding: 2rem;
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border-top: 1px solid var(--border-color);
}

.input-wrapper {
  max-width: 800px;
  margin: 0 auto;
  position: relative;
}

input[type="text"] {
  width: 100%;
  padding: 1rem 3.5rem 1rem 1.5rem;
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  color: var(--text-main);
  outline: none;
  transition: border-color 0.2s;
}

input[type="text"]:focus {
  border-color: var(--accent-primary);
}

.send-btn {
  position: absolute;
  right: 0.75rem;
  top: 50%;
  transform: translateY(-50%);
  background: transparent;
  border: none;
  color: var(--accent-primary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Topic Selection Grid */
.selection-screen {
  position: absolute;
  inset: 0;
  background: var(--bg-color);
  z-index: 20;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1.5rem;
  width: 100%;
  max-width: 1000px;
  margin-top: 2rem;
}

.card {
  background: var(--card-bg);
  padding: 2rem;
  border-radius: 1rem;
  border: 1px solid var(--border-color);
  text-align: center;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.card:hover {
  transform: translateY(-5px);
  border-color: var(--accent-primary);
  box-shadow: 0 10px 25px -5px rgba(59, 130, 246, 0.2);
}

.status-badge {
  font-size: 0.75rem;
  padding: 0.25rem 0.75rem;
  border-radius: 1rem;
  text-transform: uppercase;
  font-weight: bold;
}

.status-pass { background: rgba(16, 185, 129, 0.2); color: var(--success); }
.hint-level { background: rgba(245, 158, 11, 0.2); color: var(--warning); }

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

/* Markdown styling */
.prose h1, .prose h2, .prose h3 { margin-bottom: 1rem; }
.prose p { margin-bottom: 0.75rem; }
.prose code { background: #000; padding: 0.2rem 0.4rem; border-radius: 0.25rem; }