アイコンのみに切り替わるナビ

<div class="d03-11-05-stage">
          <header class="d03-11-05-header">
            <span class="d03-11-05-logo">ICONA</span>
            <nav class="d03-11-05-nav">
              <a href="#" onclick="return false"><i class="d03-11-05-ic d03-11-05-ic-home"></i><b>ホーム</b></a>
              <a href="#" onclick="return false"><i class="d03-11-05-ic d03-11-05-ic-serv"></i><b>サービス</b></a>
              <a href="#" onclick="return false"><i class="d03-11-05-ic d03-11-05-ic-mail"></i><b>お問合せ</b></a>
            </nav>
          </header>
          <div class="d03-11-05-scroll">
            <div class="d03-11-05-body">
              <p>↓ スクロールでナビ項目がアイコンだけに切り替わります</p>
              <div class="d03-11-05-block"></div>
              <div class="d03-11-05-block"></div>
              <div class="d03-11-05-block"></div>
              <div class="d03-11-05-block"></div>
            </div>
          </div>
        </div>

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        .d03-11-05-body p{font-size:11.5px;color:#9d174d;margin:0 0 12px;text-align:center}
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          height:80px;border-radius:8px;margin-bottom:12px;
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