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

:root {
    --primary: #6200ee;
    --primary-variant: #3700b3;
    --secondary: #03dac6;
    --background: #f5f5f5;
    --surface: #ffffff;
    --error: #b00020;
    --on-primary: #ffffff;
    --on-secondary: #000000;
    --on-background: #000000;
    --on-surface: #000000;
    --on-surface-variant: #757575;
    --outline: #e0e0e0;
    --shadow-1: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.08);
    --shadow-2: 0 4px 6px rgba(0,0,0,0.1), 0 2px 4px rgba(0,0,0,0.06);
    --shadow-3: 0 10px 20px rgba(0,0,0,0.1), 0 6px 6px rgba(0,0,0,0.1);
    --radius: 8px;
    --radius-sm: 4px;
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Roboto', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--background);
    color: var(--on-background);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding-top: 48px;
    padding-bottom: 48px;
}

.container {
    width: 100%;
    max-width: 520px;
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-3);
    overflow: hidden;
}

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

.app-header h1 {
    font-size: 24px;
    font-weight: 500;
    color: var(--on-surface);
}

.todo-count {
    font-size: 14px;
    color: var(--on-surface-variant);
}

.todo-form {
    display: flex;
    gap: 12px;
    padding: 16px 24px;
    border-bottom: 1px solid var(--outline);
}

.todo-input {
    flex: 1;
    border: none;
    outline: none;
    font-size: 16px;
    color: var(--on-surface);
    background: transparent;
    padding: 8px 0;
}

.todo-input::placeholder {
    color: var(--on-surface-variant);
}

.fab {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: none;
    background: var(--primary);
    color: var(--on-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-1);
    transition: transform var(--transition), box-shadow var(--transition);
    flex-shrink: 0;
}

.fab:hover {
    box-shadow: var(--shadow-2);
    transform: scale(1.05);
}

.fab:active {
    transform: scale(0.95);
}

.fab .material-icons {
    font-size: 24px;
}

.todo-list {
    list-style: none;
    max-height: 400px;
    overflow-y: auto;
}

.todo-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 24px;
    border-bottom: 1px solid var(--outline);
    transition: background var(--transition);
    animation: slideIn 0.3s var(--transition);
}

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

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

.todo-item.completed .todo-text {
    text-decoration: line-through;
    color: var(--on-surface-variant);
}

.todo-checkbox {
    width: 24px;
    height: 24px;
    border: 2px solid var(--outline);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
    flex-shrink: 0;
}

.todo-checkbox:hover {
    border-color: var(--primary);
}

.todo-checkbox.checked {
    background: var(--primary);
    border-color: var(--primary);
}

.todo-checkbox.checked .material-icons {
    color: var(--on-primary);
    font-size: 18px;
}

.todo-text {
    flex: 1;
    font-size: 16px;
    color: var(--on-surface);
    word-break: break-word;
    transition: color var(--transition);
}

.todo-delete {
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: var(--on-surface-variant);
    cursor: pointer;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition), color var(--transition);
    flex-shrink: 0;
}

.todo-delete:hover {
    background: rgba(0,0,0,0.08);
    color: var(--error);
}

.todo-delete .material-icons {
    font-size: 20px;
}

.app-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 24px;
    border-top: 1px solid var(--outline);
    flex-wrap: wrap;
    gap: 12px;
}

.filters {
    display: flex;
    gap: 8px;
}

.filter-btn {
    padding: 6px 12px;
    border: none;
    background: transparent;
    color: var(--on-surface-variant);
    font-size: 14px;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition);
}

.filter-btn:hover {
    background: rgba(0,0,0,0.08);
    color: var(--on-surface);
}

.filter-btn.active {
    color: var(--primary);
    font-weight: 500;
}

.clear-completed {
    padding: 8px 16px;
    border: none;
    background: transparent;
    color: var(--on-surface-variant);
    font-size: 14px;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition);
}

.clear-completed:hover {
    background: rgba(0,0,0,0.08);
    color: var(--error);
}

.empty-state {
    padding: 48px 24px;
    text-align: center;
    color: var(--on-surface-variant);
}

.empty-state .material-icons {
    font-size: 64px;
    margin-bottom: 16px;
    opacity: 0.5;
}

@media (max-width: 480px) {
    body {
        padding-top: 16px;
        padding-bottom: 16px;
    }

    .container {
        border-radius: 0;
        min-height: 100vh;
        max-width: 100%;
    }

    .app-header {
        padding: 16px;
    }

    .todo-form {
        padding: 12px 16px;
    }

    .todo-item {
        padding: 12px 16px;
    }

    .app-footer {
        padding: 12px 16px;
    }
}