* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: sans-serif;
}

body {
    background: #f5f5f5;
    padding: 20px;
    color: #333;
}

h1, h2, h3 {
    font-weight: 500;
}

.controls {
    display: flex;
    gap: 10px;
    align-items: center;
    flex-wrap: wrap;
    margin-bottom: 20px;
}

input, select {
    padding: 8px 12px;
    border: 0.5px solid #ccc;
    border-radius: 8px;
    font-size: 14px;
    background: white;
}

.lesson-card {
    background: white;
    border: 0.5px solid #ddd;
    border-radius: 12px;
    padding: 16px;
    margin-bottom: 16px;
}

button {
    padding: 8px 16px;
    border: 0.5px solid #ccc;
    border-radius: 8px;
    background: white;
    cursor: pointer;
    font-size: 14px;
    margin-top: 10px;
}

button:hover {
    background: #f0f0f0;
}

button:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.error {
    color: #E24B4A;
    font-size: 13px;
    margin-top: 4px;
}

.input-error {
    border-color: #E24B4A;
}