:root {
    --image-width: 400px; /* Width of a single image */
    --image-height: 300px; /* Height of a single image */
    --image-url: url('images/main-puzzle-image.jpg'); /* !!! UPDATE THIS PATH !!! */
}

body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: #f0f4f8;
    color: #333;
}

#game-container {
    background-color: white;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
    text-align: center;
    max-width: calc(2 * var(--image-width) + 80px); /* 2 images + gap + padding */
    width: 90%;
}

h1 {
    color: #007bff;
    margin-bottom: 20px;
}

#status-area {
    font-size: 1.2em;
    font-weight: 600;
    margin-bottom: 20px;
}

/* --- Puzzle Area and Images --- */
#puzzle-area {
    display: flex;
    gap: 20px;
    margin-bottom: 20px;
    position: relative; /* Crucial for positioning the markers absolutely */
    padding: 10px;
    border: 2px solid #ccc;
    border-radius: 8px;
}

.image-box {
    width: var(--image-width);
    height: var(--image-height);
    background-image: var(--image-url);
    background-size: cover;
    border: 1px solid #999;
    position: relative;
}

/* The invisible layer for intercepting clicks */
.clickable-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 10;
    /* We only listen for clicks on the right image */
    cursor: pointer; 
}

#image-left .clickable-overlay {
    /* Clicks on the left image do nothing */
    cursor: default; 
}

/* --- Difference Marker Styling --- */
.difference-marker {
    position: absolute;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    border: 3px solid #f44336; /* Red ring */
    box-shadow: 0 0 10px rgba(255, 0, 0, 0.8);
    pointer-events: none; /* Allows clicks to pass through to the overlay */
    transition: opacity 0.3s;
    opacity: 0; /* Hidden initially */
    z-index: 20;
    /* Center the circle on the coordinate */
    transform: translate(-50%, -50%); 
}

.difference-marker.found {
    border-color: #4CAF50; /* Green when found */
    box-shadow: 0 0 10px rgba(0, 255, 0, 0.8);
    opacity: 1; /* Visible when found */
}

/* --- Feedback and Controls --- */
#feedback-message {
    min-height: 1.5em;
    margin-bottom: 20px;
}

#start-button {
    padding: 12px 25px;
    font-size: 1.2em;
    font-weight: bold;
    background-color: #28a745;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s;
}

#start-button:hover {
    background-color: #1e7e34;
}