:root {
    --background-color: oklch(98% 0.02 240);
    --text-color: oklch(20% 0.02 240);
    --accent-color: oklch(65% 0.2 260);
    --accent-color-dark: oklch(55% 0.2 260);
    --container-bg: white;
    --task-bg: oklch(95% 0.01 240);
    --danger-color: oklch(70% 0.25 25);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100vh;
    margin: 0;
    padding-top: 4rem;
}

.container {
    width: 100%;
    max-width: 500px;
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1), 0 5px 10px rgba(0, 0, 0, 0.05);
}

h1 {
    color: var(--accent-color);
    text-align: center;
    margin-bottom: 1.5rem;
}

#todo-form {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

#todo-input {
    flex-grow: 1;
    border: 2px solid var(--task-bg);
    padding: 0.8rem 1rem;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

#todo-input:focus {
    outline: none;
    border-color: var(--accent-color);
}

#todo-form button {
    background-color: var(--accent-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    font-size: 1rem;
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

#todo-form button:hover {
    background-color: var(--accent-color-dark);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}

#todo-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.todo-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    background-color: var(--task-bg);
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 0.75rem;
    transition: background-color 0.3s ease;
    cursor: pointer;
}

.todo-item:hover {
    background-color: oklch(92% 0.01 240);
}

.todo-item.completed span {
    text-decoration: line-through;
    color: oklch(60% 0.02 240);
}

.todo-item span {
    flex-grow: 1;
}

.delete-btn {
    background-color: transparent;
    border: none;
    color: var(--danger-color);
    font-size: 1.2rem;
    font-weight: bold;
    cursor: pointer;
    padding: 0.25rem;
    opacity: 0.5;
    transition: opacity 0.3s ease;
}

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