/* ============================================================
   作业图片收集器 - 样式（适配手机 / 电脑）
   ============================================================ */
:root{
  --primary:#3b6ef6;
  --primary-dark:#2f5ae0;
  --bg:#f2f4f8;
  --card:#ffffff;
  --text:#1f2937;
  --muted:#6b7280;
  --line:#e5e7eb;
  --danger:#e5484d;
  --ok:#16a34a;
  --radius:12px;
  --shadow:0 1px 3px rgba(16,24,40,.08),0 1px 2px rgba(16,24,40,.04);
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC",
    "Hiragino Sans GB","Microsoft YaHei",Roboto,Helvetica,Arial,sans-serif;
  color:var(--text);
  background:var(--bg);
  line-height:1.6;
  -webkit-text-size-adjust:100%;
}
img{max-width:100%;display:block}
a{color:var(--primary);text-decoration:none}
input,textarea,select,button{font:inherit;color:inherit}
input[readonly]{background:#f9fafb}

.alert{--padding:.8rem 1rem;padding:.8rem 1rem;border-radius:var(--radius);margin:0 0 1rem}
.alert-error{background:#fdecec;color:#b91c1c;border:1px solid #f5c2c3}
.alert-success{background:#e8f7ee;color:#15803d;border:1px solid #b7e3c8}

/* ---------- 通用按钮 ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:.4rem;
  padding:.55rem 1.05rem;border-radius:9px;border:1px solid transparent;
  background:#fff;color:var(--text);cursor:pointer;
  font-weight:500;white-space:nowrap;transition:.15s;
  border-color:var(--line);box-shadow:var(--shadow);
}
.btn:active{transform:translateY(1px)}
.btn-primary{background:var(--primary);color:#fff;border-color:var(--primary)}
.btn-primary:hover{background:var(--primary-dark)}
.btn-ghost{background:transparent;box-shadow:none;border-color:var(--line)}
.btn-ghost:hover{background:#f3f4f6}
.btn-danger-ghost{background:transparent;box-shadow:none;border-color:var(--line);color:var(--danger)}
.btn-danger-ghost:hover{background:#fdecec;border-color:#f5c2c3}
.btn-block{width:100%}
.btn:disabled{opacity:.6;cursor:not-allowed}

/* spinner */
.spinner{
  width:16px;height:16px;border:2px solid rgba(255,255,255,.35);
  border-top-color:#fff;border-radius:50%;
  animation:spin .7s linear infinite;
}
@keyframes spin{to{transform:rotate(360deg)}}

/* ---------- 表单字段 ---------- */
.field{display:block;margin-bottom:1.1rem}
.label{display:block;font-size:.9rem;color:var(--muted);margin-bottom:.35rem;font-weight:500}
.req{color:var(--danger);font-style:normal}
.hint{display:block;font-size:.78rem;color:var(--muted);margin-top:.3rem}
input[type=text],input[type=password],input[type=file],textarea{
  width:100%;padding:.7rem .85rem;border:1px solid var(--line);
  border-radius:9px;background:#fff;outline:none;transition:.15s;
}
input:focus,textarea:focus{border-color:var(--primary);box-shadow:0 0 0 3px rgba(59,110,246,.15)}
input[type=file]{padding:.55rem;cursor:pointer}
textarea{resize:vertical}

/* 图片预览 */
.preview{
  margin-top:.6rem;border-radius:9px;border:1px solid var(--line);
  max-height:260px;object-fit:contain;background:#f9fafb;
}
.preview[hidden]{display:none}

/* ---------- 收集页（学生端） ---------- */
.collect-page{
  min-height:100vh;display:flex;align-items:center;justify-content:center;
  padding:1rem;
  background:linear-gradient(135deg,#eef2ff 0%,#f8fafc 50%,#eef2ff 100%);
}
.box{
  background:var(--card);border-radius:16px;box-shadow:0 10px 40px rgba(16,24,40,.12);
  padding:1.6rem;width:100%;max-width:520px;
}
.box-sm{max-width:400px}
.box-head{margin-bottom:1.2rem}
.box-title{margin:0 0 .35rem;font-size:1.35rem}
.box-title.is-dim{color:var(--muted)}
.box-desc{margin:0;color:var(--muted);font-size:.95rem}
.center{text-align:center;margin-top:1rem}

/* ---------- 管理后台 ---------- */
.admin-page{background:var(--bg)}
.container{max-width:1000px;margin:0 auto;padding:1rem}
.container .card{margin-bottom:1.2rem}

.topbar{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10}
.topbar-inner{
  max-width:1000px;margin:0 auto;padding:.7rem 1rem;
  display:flex;align-items:center;justify-content:space-between;gap:1rem;
}
.brand{font-weight:700;color:var(--text)}

.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:1.2rem}
.card-title{margin:0 0 1rem;font-size:1.05rem}
.empty{color:var(--muted);text-align:center;padding:1.5rem 0}

.collection-head{display:flex;flex-wrap:wrap;gap:.75rem;align-items:flex-start;justify-content:space-between;margin-bottom:.9rem}
.collection-title{margin:0 0 .3rem;font-size:1.05rem}
.collection-actions{display:flex;flex-wrap:wrap;gap:.5rem;align-items:center}
.inline-form{display:inline}
.share-row{margin-top:.3rem}
.share-input{display:flex;gap:.5rem;margin:.35rem 0 .6rem}
.share-input input{flex:1;font-size:.85rem}

.tag{display:inline-block;padding:.05rem .6rem;border-radius:999px;font-size:.75rem;font-weight:600;vertical-align:middle}
.tag-open{background:#e8f7ee;color:#15803d}
.tag-closed{background:#fdecec;color:#b91c1c}
.count{margin-left:.5rem;font-size:.85rem;color:var(--muted)}
.date{font-size:.78rem;color:var(--muted);margin-left:.5rem}

/* ---------- 提交记录页 ---------- */
.view-meta{display:flex;align-items:center;gap:1rem;margin-bottom:1rem;color:var(--muted)}
.sub-grid{
  display:grid;gap:1rem;
  grid-template-columns:repeat(auto-fill,minmax(240px,1fr));
}
.sub-card{
  margin:0;background:var(--card);border-radius:var(--radius);
  box-shadow:var(--shadow);overflow:hidden;display:flex;flex-direction:column;
}
.sub-img-wrap{background:#eef0f4;display:block}
.sub-img{width:100%;height:200px;object-fit:cover;transition:transform .2s}
.sub-img-wrap:hover .sub-img{transform:scale(1.03)}
.sub-info{padding:.75rem 1rem;}
.sub-name{font-weight:600;font-size:.98rem}
.sub-desc{font-size:.85rem;color:var(--text);margin:.3rem 0;padding:.4rem .6rem;background:#f9fafb;border-radius:6px;border-left:3px solid var(--primary);}
.sub-time,.sub-ip,.sub-ua{font-size:.8rem;color:var(--muted);word-break:break-all;}
.sub-ua{white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.sub-dl{display:inline-block;margin-top:.5rem;font-size:.85rem}

/* ============================================================
   响应式：手机端排版优化
   ============================================================ */
@media (max-width:720px){
  .box{padding:1.2rem}
  .box-title{font-size:1.15rem}

  .collection-head{flex-direction:column}
  .collection-actions{width:100%}
  .collection-actions .btn{flex:1;justify-content:center}
  .share-input{flex-direction:column}
  .share-input input{font-size:.8rem;text-align:center}
  .share-row .btn{width:100%}

  .sub-grid{grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:.75rem}
  .sub-img{height:150px}
  .sub-info{padding:.6rem .75rem}
  .sub-ip,.sub-ua{font-size:.72rem}

  .topbar-inner{padding:.6rem .75rem}
  .brand{font-size:.9rem}
  .topbar-inner .btn{padding:.4rem .75rem;font-size:.85rem}

  .create-form input,.create-form textarea{font-size:1rem} /* 防止 iOS 缩放 */
}