.detail-page{background-color:#f9fafb;min-height:100vh;padding-bottom:4rem}.detail-header{background:linear-gradient(90deg,#4f46e5,#9333ea);color:#fff;text-align:center;padding:3rem 1rem 2rem;box-shadow:0 4px 12px rgba(0,0,0,.1)}.detail-header h1{font-size:2rem;font-weight:800;margin-bottom:.25rem}.detail-header .category{font-size:.95rem;color:#e0e7ff}.letter-container{max-width:800px;margin:-2rem auto 0;background:#fff;padding:2rem;border-radius:12px;box-shadow:0 4px 20px rgba(0,0,0,.06);line-height:1.7}.letter-line{margin-bottom:1rem;font-size:1rem;color:#374151;white-space:pre-wrap}.copy-btn{background:linear-gradient(90deg,#4f46e5,#9333ea);color:#fff;padding:10px;border-radius:10px}