/* =========================================
   1. ОБЩИЕ СТИЛИ И МЕНЮ
   ========================================= */
* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font-family: 'Segoe UI', sans-serif;
    background: #f8f9fa;
    min-height: 100vh;
    color: #333;
}

/* ЗАГОЛОВОК ВЕРХУ */
.top-header {
    background: white;
    padding: 20px 30px;
    border-bottom: 2px solid #3498db;
    position: fixed;
    top: 0; left: 260px;
    right: 0;
    z-index: 100;
}

.header-text {
    color: #2980b9;
    font-size: 20px;
    font-weight: 600;
}

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

/* БОКОВОЕ МЕНЮ */
.sidebar {
    width: 260px;
    background: #f0f4f8;
    padding: 80px 20px 20px 20px;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
    border-right: 1px solid #ddd;
}

.menu-btn {
    width: 100%;
    padding: 15px;
    margin-bottom: 10px;
    background: white;
    border: 2px solid #3498db;
    border-radius: 8px;
    color: #2c3e50;
    font-weight: bold;
    font-style: italic;
    font-size: 15px;
    text-align: left;
    cursor: pointer;
    transition: 0.3s;
}

.menu-btn:hover {
    background: #3498db;
    color: white;
}

.menu-btn.active {
    background: #2980b9;
    color: white;
    box-shadow: 0 4px 10px rgba(52, 152, 219, 0.3);
}

/* ОСНОВНАЯ ОБЛАСТЬ */
.main-content {
    margin-left: 260px;
    padding: 90px 40px 40px 40px;
    width: calc(100% - 260px);
    max-width: 1000px;
}

.section { display: none; }
.section.active { display: block; }

.placeholder {
    background: white; padding: 30px; border-radius: 10px;
    text-align: center; color: #999; margin-top: 20px;
    border: 1px dashed #ccc;
}