BFE.devでのAI解答例 - CSS 質問
17. fragment style

.border { line-height: 1.5; margin: 5px; display: inline-block; /* to enable padding */ }

.border::first-line { border-top: 1px solid #7aa4f0; }

.border::last-line { border-bottom: 1px solid #7aa4f0; }

.border:not(::first-line)::not(::last-line) { border-top: 1px solid #7aa4f0; padding-top: 5px; padding-bottom: 5px; }