:root {
    --primary-bg: #f4f4f9;
    --secondary-bg: #ffffff;
    --text-color: #333;
    --primary-color: #007bff;
    --border-color: #ddd;
    --danger-color: #dc3545;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--primary-bg);
    color: var(--text-color);
    margin: 0;
    padding: 1rem;
    line-height: 1.5;
}

#app {
    max-width: 800px;
    margin: 0 auto;
}

header {
    margin-bottom: 1.5rem;
    text-align: center;
}

.user-info {
    font-size: 0.9rem;
    color: #666;
}

.badge {
    background-color: var(--primary-color);
    color: white;
    padding: 0.2rem 0.5rem;
    border-radius: 8px;
    font-size: 0.8rem;
    margin-left: 0.5rem;
}

section {
    background-color: var(--secondary-bg);
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

h1, h2 {
    margin: 0 0 1rem 0;
    color: #000;
}

.controls .filters {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

select, input, textarea, button {
    width: 100%;
    padding: 0.75rem;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    font-size: 1rem;
    box-sizing: border-box;
}

button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    cursor: pointer;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #0056b3;
}

#homework-list .card {
    border: 1px solid var(--border-color);
    padding: 1rem;
    border-radius: 6px;
    margin-bottom: 1rem;
    position: relative;
}

#homework-list .card h3 {
    margin: 0 0 0.5rem;
}

#homework-list .card .delete-hw-btn {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    background-color: var(--danger-color);
    color: white;
    border: none;
    border-radius: 50%;
    width: 24px;
    height: 24px;
    cursor: pointer;
    font-weight: bold;
}

#add-hw-form {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

/* Loader */
#loader {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(255, 255, 255, 0.8);
    display: none;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    z-index: 1000;
}
#loader.active {
    display: flex;
}
.spinner {
    border: 4px solid #f3f3f3;
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}
@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 1;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.4);
}
.modal-content {
    background-color: #fefefe;
    margin: 15% auto;
    padding: 20px;
    border: 1px solid #888;
    width: 80%;
    max-width: 500px;
    border-radius: 8px;
    text-align: center;
}
.modal-content select, .modal-content button {
    margin-top: 1rem;
}