body { font-family: sans-serif; text-align: center; margin-top: 50px; background-color: #f4f4f9; }
        
        #stats-box { 
            position: fixed; top: 10px; left: 10px; text-align: left; 
            background: white; padding: 10px; border-radius: 8px; 
            box-shadow: 0 2px 4px rgba(0,0,0,0.1); border: 1px solid #ddd; 
            font-size: 0.85em; color: #333; z-index: 100; 
        }

        .quiz-container { 
            background: white; padding: 30px; border-radius: 15px; 
            display: inline-block; box-shadow: 0 4px 6px rgba(0,0,0,0.1); 
            width: 380px; position: relative; 
        }
        
        h1 { color: #333; font-size: 1.5em; margin-bottom: 5px; }
        
        .equation-display { 
            font-size: 2em; font-family: 'Courier New', Courier, monospace; 
            margin: 25px; color: #333; font-weight: bold; min-height: 80px; 
            display: flex; align-items: center; justify-content: center; 
        }
        
        #button-group { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
        
        button { 
            padding: 15px; font-size: 1.1em; cursor: pointer; border-radius: 8px; 
            border: 1px solid #ddd; background: #fff; transition: 0.2s; font-weight: bold; 
        }
        
        button:hover { background: #eee; }
        
        #feedback { margin-top: 20px; font-weight: bold; min-height: 1.5em; line-height: 1.4; }
        .correct { color: green; }
        .incorrect { color: red; }
        
        .hidden { display: none; }
        #nextBtn { 
            background-color: #e7f3ff; border: 1px solid #b2d7ff; 
            font-weight: bold; color: #333; grid-column: span 2; margin-top: 10px; 
            padding: 12px; cursor: pointer; border-radius: 8px;
        }
        
        .back-link { 
            display: inline-block; margin-top: 20px; text-decoration: none; 
            color: #777; font-size: 0.8em; font-weight: bold; 
        }
        .axis-display {
    font-size: 2em;
    font-family: 'Courier New', Courier, monospace;
    margin: 25px;
    color: #333;
    font-weight: bold;
    min-height: 80px;
    display: flex;
    align-items: center;
    justify-content: center;
}
#equation {
    font-size: 1.8em;           /* big enough for visibility */
    font-family: 'Courier New', Courier, monospace;
    font-weight: bold;
    min-height: 90px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #333;
}