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

body, html {
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    background-color: #f4f4f9;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

/* The "Instruction" Layer - Front and Center */
.instruction-layer {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 100; /* Higher than heatmap */
    pointer-events: none; /* Mouse moves "pass through" this text */
    text-align: center;
}

h1 {
    font-size: 3rem;
    color: rgba(0,0,0,0.2); /* Faded so heatmap is visible through it */
    text-transform: uppercase;
    letter-spacing: 5px;
}

/* The Heatmap Layer */
#heatmap-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: 1; /* Below the text */
    pointer-events: none;
}

/* The Admin Button */
#clear-btn {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
    padding: 10px 20px;
    background: #ff4757;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: bold;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    
    /* The Opacity Logic */
    opacity: 0; 
    pointer-events: none; 
    transition: opacity 0.5s ease-in-out; 
}

/* When this class is added via JS, the button fades in */
#clear-btn.visible {
    opacity: 1;
    pointer-events: auto;
}