.stu-container {
    background: #0f172a;
    color: #f8fafc;
    border-radius: 15px;
    padding: 30px;
    max-width: 600px;
    margin: 20px auto;
    font-family: 'Segoe UI', sans-serif;
    text-align: center;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

.stu-header h3 { margin: 0 0 5px 0; color: #fff; }
#stu-status { font-size: 0.9em; color: #94a3b8; margin-bottom: 20px; }

/* Gauge */
.stu-gauge-wrapper {
    position: relative;
    width: 200px; height: 100px;
    margin: 0 auto 30px;
    overflow: hidden;
}
.stu-gauge-arc {
    width: 200px; height: 200px;
    background: conic-gradient(from 270deg, #06b6d4 0%, #334155 0%);
    border-radius: 50%;
    transition: background 0.2s;
}
.stu-gauge-cover {
    position: absolute;
    top: 15px; left: 15px;
    width: 170px; height: 170px;
    background: #0f172a;
    border-radius: 50%;
    display: flex; flex-direction: column;
    justify-content: center; align-items: center;
}
.stu-live-speed { font-size: 2.5em; font-weight: bold; line-height: 1; }
.stu-unit { font-size: 0.8em; color: #64748b; }

/* Button */
#stuStartBtn {
    background: transparent;
    border: 2px solid #06b6d4;
    color: #06b6d4;
    padding: 15px 40px;
    font-size: 1.2em;
    border-radius: 50px;
    cursor: pointer;
    transition: 0.3s;
    font-weight: bold;
}
#stuStartBtn:hover { background: #06b6d4; color: #fff; box-shadow: 0 0 20px rgba(6,182,212,0.4); }
#stuStartBtn.hidden { display: none; }

/* Grid */
.stu-stats-grid {
    display: flex; justify-content: space-between; margin-top: 30px;
    border-top: 1px solid #334155; padding-top: 20px;
}
.stu-stat-box { width: 30%; }
.stu-label { display: block; font-size: 0.75em; color: #64748b; letter-spacing: 1px; }
.stu-value { display: block; font-size: 1.4em; font-weight: bold; margin-top: 5px; }
.stu-unit-small { font-size: 0.7em; color: #475569; }