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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
    width: 100%;
    max-width: 900px;
    padding: 40px;
    animation: fadeIn 0.5s ease-in;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

h1 {
    color: #667eea;
    text-align: center;
    margin-bottom: 30px;
    font-size: 2em;
}

h2 {
    color: #555;
    margin-bottom: 20px;
    font-size: 1.5em;
}

.form-group {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 8px;
    color: #555;
    font-weight: 600;
}

input, select {
    width: 100%;
    padding: 12px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 16px;
    transition: border-color 0.3s;
}

input:focus, select:focus {
    outline: none;
    border-color: #667eea;
}

button {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 14px 28px;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    width: 100%;
    margin-top: 10px;
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

button:active {
    transform: translateY(0);
}

.btn-secondary {
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    margin-top: 10px;
}

.btn-secondary:hover {
    box-shadow: 0 5px 15px rgba(245, 87, 108, 0.4);
}

.hidden {
    display: none;
}

.lesson-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.lesson-card {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    border: 2px solid #e0e0e0;
    transition: transform 0.2s, box-shadow 0.2s;
}

.lesson-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

.lesson-card h3 {
    color: #667eea;
    margin-bottom: 15px;
    font-size: 1.1em;
}

.input-row {
    display: flex;
    gap: 10px;
    margin-bottom: 10px;
}

.input-row input {
    flex: 1;
}

.extra-activities {
    background: #fff3cd;
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 20px;
    border-left: 4px solid #ffc107;
}

.success-message {
    background: #d4edda;
    color: #155724;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
    text-align: center;
    border-left: 4px solid #28a745;
    animation: slideDown 0.3s ease-out;
}

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

.error-message {
    background: #f8d7da;
    color: #721c24;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
    text-align: center;
    border-left: 4px solid #dc3545;
}

.student-list {
    margin-top: 20px;
}

.student-card {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 15px;
    border-left: 4px solid #667eea;
    transition: transform 0.2s;
}

.student-card:hover {
    transform: translateX(5px);
    box-shadow: 0 3px 10px rgba(0,0,0,0.1);
}

.student-card h3 {
    color: #667eea;
    margin-bottom: 15px;
}

.activity-item {
    padding: 8px 0;
    border-bottom: 1px solid #e0e0e0;
    display: flex;
    justify-content: space-between;
}

.activity-item:last-child {
    border-bottom: none;
}

.activity-item strong {
    color: #555;
}

.no-data {
    text-align: center;
    color: #999;
    padding: 40px;
    font-size: 1.2em;
}

.user-info {
    background: #e7f3ff;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
    text-align: center;
    border-left: 4px solid #2196F3;
}

.tab-buttons {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.tab-buttons button {
    flex: 1;
}

.loading {
    text-align: center;
    padding: 20px;
    color: #667eea;
}

.loading::after {
    content: '...';
    animation: dots 1.5s steps(4, end) infinite;
}

@keyframes dots {
    0%, 20% {
        content: '.';
    }
    40% {
        content: '..';
    }
    60%, 100% {
        content: '...';
    }
}

@media (max-width: 768px) {
    .container {
        padding: 20px;
    }
    
    h1 {
        font-size: 1.5em;
    }
    
    .lesson-grid {
        grid-template-columns: 1fr;
    }

    .tab-buttons {
        flex-direction: column;
    }
}