/* Default (Light Theme) Variables */
:root {
    --body-bg: #ffffff;
    --todo-container-bg: #dbdbdb;
    --h1-color: #333;
    --input-border-color: #ddd;
    --input-focus-border-color: #007bff;
    --button-bg: #007bff;
    --button-hover-bg: #0056b3;
    --button-text-color: white;
    --todo-item-bg: #f8f9fa;
    --todo-item-hover-bg: #e9ecef;
    --todo-item-border-left: #007bff;
    --todo-item-completed-border-left: #28a745;
    --delete-btn-bg: #dc3545;
    --delete-btn-hover-bg: #c82333;
    --empty-state-color: #6c757d;
    --theme-toggle-bg: #6c757d;
    --theme-toggle-hover-bg: #5a6268;
}

/* Dark Theme Variables */
body.dark-theme {
    --body-bg: #2c2c2c; /* Darker background */
    --todo-container-bg: #444444; /* Darker container */
    --h1-color: #f0f0f0; /* Light text for headings */
    --input-border-color: #555;
    --input-focus-border-color: #66b3ff;
    --button-bg: #4CAF50; /* Green for add button */
    --button-hover-bg: #45a049;
    --button-text-color: white;
    --todo-item-bg: #555555; /* Darker todo item background */
    --todo-item-hover-bg: #666666;
    --todo-item-border-left: #4CAF50; /* Green border for active tasks */
    --todo-item-completed-border-left: #77c27a; /* Lighter green for completed */
    --delete-btn-bg: #e74c3c; /* Red for delete button */
    --delete-btn-hover-bg: #c0392b;
    --empty-state-color: #bbb;
    --theme-toggle-bg: #007bff; /* Blue for toggle button */
    --theme-toggle-hover-bg: #0056b3;
}


/* General Styling - Use variables */
body {
    margin: 0;
    padding: 0;
    font-family: Arial, sans-serif;
    background: var(--body-bg); /* Use variable for theme support */
    min-height: 100vh;
    box-sizing: border-box;
}

.todo-container {
    max-width: 400px;
    margin: 40px auto;
    padding: 20px;
    background: var(--todo-container-bg); /* Use variable for theme support */
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

h1 {
    text-align: center;
    color: var(--h1-color); /* Use variable */
    margin-bottom: 30px;
}

.input-section {
    display: flex;
    flex-direction: row;
    gap: 8px;
    margin-bottom: 16px;
}

.input-section input[type="text"] {
    flex: 1;
    padding: 10px;
    font-size: 1rem;
    border: 1px solid #ccc;
    border-radius: 4px;
}

.input-section button {
    padding: 10px 16px;
    font-size: 1rem;
    border: none;
    border-radius: 4px;
    background: #007bff;
    color: #fff;
    cursor: pointer;
}

.input-section button:active {
    background: #0056b3;
}

button {
    padding: 12px 20px;
    background: var(--button-bg); /* Use variable */
    color: var(--button-text-color); /* Use variable */
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s;
}

button:hover {
    background: var(--button-hover-bg); /* Use variable */
}

.todo-item {
    background: var(--todo-item-bg); /* Use variable */
    padding: 15px;
    margin: 10px 0;
    border-radius: 6px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-left: 4px solid var(--todo-item-border-left); /* Use variable */
    transition: all 0.3s;
    color: var(--h1-color); /* Ensure todo text is readable */
}

.todo-item:hover {
    background: var(--todo-item-hover-bg); /* Use variable */
}

.todo-item.completed {
    text-decoration: line-through;
    opacity: 0.6;
    border-left-color: var(--todo-item-completed-border-left); /* Use variable */
}

.todo-text {
    cursor: pointer;
    flex: 1;
    font-size: 16px;
    user-select: none;
}

.delete-btn {
    background: var(--delete-btn-bg); /* Use variable */
    padding: 8px 12px;
    font-size: 14px;
    margin-left: 10px;
}

.delete-btn:hover {
    background: var(--delete-btn-hover-bg); /* Use variable */
}

.empty-state {
    text-align: center;
    color: var(--empty-state-color); /* Use variable */
    font-style: italic;
    margin-top: 30px;
}

/* New: Theme Toggle Button Specific Style */
.theme-toggle-btn {
    display: block;
    margin: 0 auto 20px auto; /* Center the button and add space below */
    background-color: var(--theme-toggle-bg);
    color: var(--button-text-color);
    padding: 10px 15px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: background-color 0.3s ease;
}

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

@media (max-width: 500px) {
    body {
        padding: 8px;
        /* Prevent horizontal scroll */
        overflow-x: hidden;
    }
    .todo-container {
        max-width: 100%;
        margin: 0;
        border-radius: 0;
        box-shadow: none;
        padding: 10px 4px;
    }
    .input-section {
        flex-direction: column;
        gap: 8px;
    }
    .input-section button,
    .input-section input[type="text"] {
        width: 100%;
        font-size: 1.1rem;
        min-height: 44px; /* Easier tap targets */
        box-sizing: border-box;
    }
    button,
    .theme-toggle-btn {
        font-size: 1rem;
        min-height: 44px;
    }
    h1 {
        font-size: 1.3rem;
        margin-bottom: 18px;
    }
    .todo-item {
        font-size: 1rem;
        padding: 12px 8px;
    }
}