:root {
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --text: #1e293b;
    --text-secondary: #64748b;
    --border: #e2e8f0;
    --success: #22c55e;
    --danger: #ef4444;
    --warning: #f59e0b;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 600px;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

h1 {
    font-size: 1.8rem;
    color: var(--text);
}

.sync-status {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: 20px;
    background: var(--card-bg);
    font-size: 0.85rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.sync-status.online {
    background: #dcfce7;
}

.sync-status.online .status-icon {
    content: '🟢';
}

.sync-status.offline {
    background: #fee2e2;
}

.mode-selector {
    background: var(--card-bg);
    padding: 15px 20px;
    border-radius: 12px;
    margin-bottom: 20px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.mode-selector label {
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
    font-weight: 500;
}

.mode-selector input[type="checkbox"] {
    width: 20px;
    height: 20px;
    accent-color: var(--primary);
}

.input-section {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

#taskInput {
    flex: 1;
    padding: 14px 18px;
    border: 2px solid var(--border);
    border-radius: 10px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

#taskInput:focus {
    outline: none;
    border-color: var(--primary);
}

#addBtn {
    padding: 14px 24px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}

#addBtn:hover {
    background: var(--primary-hover);
}

.filters {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
    flex-wrap: wrap;
    align-items: center;
}

.filter-btn {
    padding: 8px 16px;
    border: none;
    border-radius: 8px;
    background: var(--card-bg);
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
}

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

.filter-btn:hover:not(.active) {
    background: var(--border);
}

.clear-completed {
    margin-left: auto;
    padding: 8px 16px;
    background: transparent;
    border: 1px solid var(--danger);
    color: var(--danger);
    border-radius: 8px;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s;
}

.clear-completed:hover {
    background: var(--danger);
    color: white;
}

.stats {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 15px;
}

.task-list {
    list-style: none;
}

.task-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 15px 18px;
    background: var(--card-bg);
    border-radius: 10px;
    margin-bottom: 10px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    animation: slideIn 0.3s ease;
}

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

.task-item input[type="checkbox"] {
    width: 22px;
    height: 22px;
    accent-color: var(--primary);
    cursor: pointer;
}

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

.task-item span {
    flex: 1;
    font-size: 1rem;
}

.delete-btn {
    padding: 8px 12px;
    background: transparent;
    border: none;
    color: var(--danger);
    font-size: 1.2rem;
    cursor: pointer;
    opacity: 0.6;
    transition: opacity 0.2s;
}

.delete-btn:hover {
    opacity: 1;
}

footer {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-top: 30px;
}

.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
}

.empty-state span {
    font-size: 3rem;
    display: block;
    margin-bottom: 10px;
}

.syncing {
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}