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

:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
}

.auth-page {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 20px;
}

.auth-container {
    width: 100%;
    max-width: 420px;
}

.auth-card {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 40px;
    box-shadow: var(--shadow-lg);
}

.auth-header {
    text-align: center;
    margin-bottom: 30px;
}

.auth-header h1 {
    font-size: 32px;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.auth-header p {
    color: var(--text-secondary);
    font-size: 14px;
}

.auth-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--border-color);
}

.tab-btn {
    flex: 1;
    padding: 12px;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.2s;
}

.tab-btn:hover {
    color: var(--primary-color);
}

.tab-btn.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.auth-form {
    display: none;
}

.auth-form.active {
    display: block;
}

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

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.2s;
    background: var(--card-bg);
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.btn-secondary {
    background: var(--secondary-color);
    color: white;
}

.btn-secondary:hover {
    background: #475569;
}

.btn-danger {
    background: var(--danger-color);
    color: white;
}

.btn-danger:hover {
    background: #dc2626;
}

.btn-block {
    width: 100%;
}

.error-message {
    margin-top: 16px;
    padding: 12px;
    background: #fef2f2;
    border: 1px solid #fecaca;
    border-radius: 8px;
    color: #991b1b;
    font-size: 14px;
    display: none;
}

.error-message.show {
    display: block;
}

.todos-page {
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.header {
    background: var(--card-bg);
    box-shadow: var(--shadow);
    margin-bottom: 24px;
    padding: 20px 0;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header h1 {
    font-size: 28px;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.username {
    color: var(--text-secondary);
    font-size: 14px;
}

.main-content {
    padding-bottom: 40px;
}

.add-todo-section {
    background: var(--card-bg);
    padding: 24px;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 24px;
}

.add-todo-form {
    width: 100%;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr auto auto auto;
    gap: 12px;
    align-items: end;
}

.todo-input {
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.2s;
}

.todo-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.todo-date,
.todo-priority {
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    background: var(--card-bg);
    cursor: pointer;
    transition: all 0.2s;
}

.todo-date:focus,
.todo-priority:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.filters {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
}

.filter-btn {
    padding: 8px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background: var(--card-bg);
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.filter-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.filter-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.todos-container {
    display: grid;
    gap: 12px;
}

.todo-item {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 12px;
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 16px;
    transition: all 0.2s;
    border-left: 4px solid transparent;
}

.todo-item:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.todo-item.completed {
    opacity: 0.7;
}

.todo-item.priority-low {
    border-left-color: var(--success-color);
}

.todo-item.priority-medium {
    border-left-color: var(--warning-color);
}

.todo-item.priority-high {
    border-left-color: var(--danger-color);
}

.todo-checkbox {
    width: 24px;
    height: 24px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.todo-content {
    flex: 1;
    min-width: 0;
}

.todo-title {
    font-size: 16px;
    font-weight: 500;
    margin-bottom: 4px;
    word-break: break-word;
}

.todo-item.completed .todo-title {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.todo-meta {
    display: flex;
    gap: 16px;
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 4px;
}

.todo-actions {
    display: flex;
    gap: 8px;
}

.btn-icon {
    padding: 8px;
    background: none;
    border: none;
    cursor: pointer;
    border-radius: 6px;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
}

.btn-icon:hover {
    background: var(--bg-color);
}

.btn-edit:hover {
    color: var(--primary-color);
}

.btn-delete:hover {
    color: var(--danger-color);
}

.loading,
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
    font-size: 16px;
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: var(--card-bg);
    border-radius: 12px;
    width: 100%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h2 {
    font-size: 20px;
}

.modal-close {
    background: none;
    border: none;
    font-size: 28px;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    transition: all 0.2s;
}

.modal-close:hover {
    background: var(--bg-color);
    color: var(--text-primary);
}

.modal form {
    padding: 24px;
}

.modal-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
    margin-top: 24px;
}

@media (max-width: 768px) {
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .header-content {
        flex-direction: column;
        gap: 16px;
        align-items: flex-start;
    }
    
    .todo-item {
        flex-wrap: wrap;
    }
    
    .todo-actions {
        width: 100%;
        justify-content: flex-end;
    }
}