:root {
    --bg-color: #fdfbfb;
    --container-bg: #ffffff;
    --primary-color: #a8dadc;
    --primary-dark: #457b9d;
    --accent-color: #f1faee;
    --text-color: #1d3557;
    --text-light: #6c757d;
    --danger-color: #e63946;
    --shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    --radius: 16px;
}

body {
    font-family: 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    padding: 40px 20px;
    margin: 0;
}

.container {
    background: var(--container-bg);
    width: 100%;
    max-width: 500px;
    padding: 2rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    margin: 0;
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-color);
}

header p {
    margin: 0.5rem 0 0;
    color: var(--text-light);
    font-size: 1rem;
}

.input-group {
    display: flex;
    gap: 10px;
    margin-bottom: 2rem;
}

input[type="text"] {
    flex: 1;
    padding: 12px 16px;
    border: 2px solid var(--accent-color);
    border-radius: 12px;
    font-size: 1rem;
    outline: none;
    transition: border-color 0.2s;
}

input[type="text"]:focus {
    border-color: var(--primary-color);
}

button#addButton {
    background-color: var(--primary-color);
    color: var(--text-color);
    border: none;
    padding: 0 20px;
    border-radius: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
}

button#addButton:hover {
    background-color: #bde0e2;
}

button#addButton:active {
    transform: scale(0.95);
}

ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

li {
    display: flex;
    align-items: center;
    padding: 12px;
    background: var(--accent-color);
    margin-bottom: 8px;
    border-radius: 12px;
    transition: all 0.2s ease;
    border: 1px solid transparent;
}

li.completed {
    opacity: 0.6;
    background: #f8f9fa;
}

li.completed .item-text {
    text-decoration: line-through;
    color: var(--text-light);
}

.checkbox {
    width: 20px;
    height: 20px;
    margin-right: 12px;
    cursor: pointer;
    accent-color: var(--primary-dark);
}

.item-text {
    flex: 1;
    cursor: pointer;
    font-size: 1rem;
    user-select: none;
}

.delete-btn {
    background: none;
    border: none;
    color: var(--text-light);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0 8px;
    transition: color 0.2s;
}

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

.stats {
    display: flex;
    justify-content: space-between;
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--accent-color);
    font-size: 0.9rem;
    color: var(--text-light);
    font-weight: 500;
}