/* --- ПЕРЕМЕННЫЕ --- */
:root {
    --font-main: 'Inter', sans-serif;
    --font-code: 'JetBrains Mono', monospace;
    
    --bg-app: #F3F4F6;
    --bg-surface: #FFFFFF;
    
    --text-primary: #111827;
    --text-secondary: #4B5563;
    --text-muted: #9CA3AF;
    
    --brand-primary: #2563EB;
    --brand-hover: #1D4ED8;
    
    --sidebar-bg: #111827;
    --sidebar-hover: #1F2937;
    
    --border-color: #E5E7EB;
}

/* --- БАЗОВЫЕ НАСТРОЙКИ --- */
body {
    font-family: var(--font-main);
    margin: 0;
    background-color: var(--bg-app);
    color: var(--text-primary);
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
}

/* --- ВЕРХНЯЯ ПАНЕЛЬ (HEADER) --- */
.top-header {
    height: 60px;
    background-color: var(--bg-surface);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    box-sizing: border-box;
    z-index: 10;
}

.logo-area {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    color: var(--brand-primary);
}

.logo-area b { color: var(--text-primary); }

.user-badge {
    background: #E0E7FF;
    color: #3730A3;
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
}

/* --- КАРКАС ПРИЛОЖЕНИЯ --- */
.app-container {
    display: flex;
    flex: 1;
    overflow: hidden;
}

/* --- САЙДБАР --- */
.sidebar {
    width: 280px;
    background-color: var(--sidebar-bg);
    color: #F9FAFB;
    padding: 20px 16px;
    overflow-y: auto;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.menu-section h2 {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: #9CA3AF;
    margin: 0 0 8px 12px;
}

.nav-item {
    padding: 10px 12px;
    margin-bottom: 4px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    color: #D1D5DB;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-item:hover {
    background-color: var(--sidebar-hover);
    color: #FFFFFF;
}

.nav-item.active {
    background-color: var(--brand-primary);
    color: #FFFFFF;
    font-weight: 500;
}

/* --- КОНТЕНТНАЯ ЗОНА --- */
.content {
    flex: 1;
    padding: 40px;
    overflow-y: auto;
    box-sizing: border-box;
}

.task-container {
    max-width: 850px;
    margin: 0 auto;
    background: var(--bg-surface);
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    border: 1px solid var(--border-color);
}

.task-page { display: none; animation: fadeIn 0.3s ease; }
.task-page.active { display: block; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(5px); } to { opacity: 1; transform: translateY(0); } }

/* --- ТИПОГРАФИКА ВНУТРИ ЗАДАНИЙ --- */
h1 {
    font-size: 1.75rem;
    margin: 0 0 24px 0;
    color: var(--text-primary);
    font-weight: 600;
    letter-spacing: -0.02em;
}

h3 {
    font-size: 1.1rem;
    margin: 0 0 12px 0;
    color: var(--text-primary);
}

p, li {
    color: var(--text-secondary);
    line-height: 1.6;
    font-size: 0.95rem;
}

/* --- БЕЙДЖИ УРОВНЕЙ --- */
.level-badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 16px;
}
.level-1 { background: #F3F4F6; color: #4B5563; }
.level-2 { background: #DBEAFE; color: #1E40AF; }
.level-3 { background: #FEE2E2; color: #991B1B; }

/* --- ИНФОБЛОКИ (ТЕОРИЯ) --- */
details {
    background: #EFF6FF;
    border: 1px solid #BFDBFE;
    border-left: 4px solid var(--brand-primary);
    padding: 16px;
    border-radius: 6px;
    margin-bottom: 24px;
}
summary {
    font-weight: 600;
    color: #1E40AF;
    cursor: pointer;
    outline: none;
    list-style: none; /* Убираем стандартную стрелку */
}
summary::-webkit-details-marker { display: none; }
details p { margin: 12px 0 0 0; color: #1E3A8A; }

/* --- БЛОК ОПИСАНИЯ ЗАДАЧИ --- */
.task-box {
    background: #F9FAFB;
    border: 1px solid var(--border-color);
    padding: 24px;
    border-radius: 8px;
    margin-bottom: 24px;
}

/* --- КОД И РЕШЕНИЯ --- */
code {
    font-family: var(--font-code);
    background: #F3F4F6;
    padding: 2px 6px;
    border-radius: 4px;
    color: #DC2626;
    font-size: 0.85em;
    border: 1px solid #E5E7EB;
}

pre { margin: 0; }
pre code {
    display: block;
    background: #1E1E1E;
    color: #D4D4D4;
    padding: 20px;
    border-radius: 0 0 8px 8px;
    border: none;
    font-size: 0.9rem;
    line-height: 1.5;
    overflow-x: auto;
}

/* Блок с решением */
.btn-solution {
    background: var(--bg-surface);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    padding: 10px 20px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.2s;
    box-shadow: 0 1px 2px rgba(0,0,0,0.05);
}
.btn-solution:hover {
    background: #F9FAFB;
    border-color: #D1D5DB;
}
.btn-solution.active {
    background: var(--brand-primary);
    color: white;
    border-color: var(--brand-primary);
}

.solution-box {
    display: none;
    margin-top: 16px;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.code-header {
    background: #2D2D2D;
    color: #9CA3AF;
    padding: 8px 16px;
    font-size: 0.85rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #404040;
}

.btn-copy {
    background: transparent;
    color: #D1D5DB;
    border: 1px solid #4B5563;
    padding: 4px 10px;
    border-radius: 4px;
    font-size: 0.75rem;
    cursor: pointer;
    transition: 0.2s;
}
.btn-copy:hover {
    background: #4B5563;
    color: white;
}

/* Ссылки и картинки */
.external-link { color: var(--brand-primary); text-decoration: none; font-weight: 500; }
.external-link:hover { text-decoration: underline; }
.instruction-img { max-width: 100%; border-radius: 8px; border: 1px solid var(--border-color); box-shadow: 0 2px 4px rgba(0,0,0,0.05); margin: 16px 0; }