:root {
  --ink: #14131f;
  --paper: #f6f5f2;
  --panel: #ffffff;
  --line: #e4e1da;
  --accent: #4b3df0;
  --accent-soft: #ecebff;
  --muted: #6f6c63;
  --danger: #b3261e;
  --radius: 10px;
  --serif: "Source Serif Pro", Georgia, "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 32px;
  border-bottom: 1px solid var(--line);
}

.brand { display: flex; align-items: center; gap: 12px; }
.brand-mark { color: var(--accent); font-size: 22px; }
.brand-title { font-family: var(--serif); font-size: 20px; line-height: 1.1; }
.brand-sub { font-size: 12px; color: var(--muted); }

.tabs {
  display: flex;
  gap: 4px;
  padding: 16px 32px 0;
  border-bottom: 1px solid var(--line);
}

.tab {
  border: none;
  background: none;
  font: inherit;
  font-size: 14px;
  padding: 10px 16px;
  cursor: pointer;
  color: var(--muted);
  border-bottom: 2px solid transparent;
}

.tab.active { color: var(--ink); border-bottom-color: var(--accent); font-weight: 600; }

.layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 0;
  min-height: calc(100vh - 130px);
}

.panel-list {
  border-right: 1px solid var(--line);
  padding: 24px;
}

.panel-list-head h2 {
  font-family: var(--serif);
  font-size: 22px;
  margin: 0 0 4px;
}

.muted { color: var(--muted); font-size: 13px; margin: 0 0 16px; }
.muted.small { font-size: 12px; }

.file-list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 8px; }

.file-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  cursor: pointer;
}

.file-item:hover { border-color: var(--accent); }
.file-item.selected { border-color: var(--accent); background: var(--accent-soft); }

.file-ext {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--accent);
  background: var(--accent-soft);
  border-radius: 4px;
  padding: 3px 6px;
  flex-shrink: 0;
}

.file-name { font-size: 13px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; flex: 1; }

.file-delete {
  border: none;
  background: none;
  color: var(--muted);
  cursor: pointer;
  font-size: 14px;
  padding: 2px 6px;
}
.file-delete:hover { color: var(--danger); }

.empty { color: var(--muted); font-size: 13px; }
.hidden { display: none !important; }

.panel-viewer { padding: 24px; display: flex; flex-direction: column; }

.viewer-empty {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  border: 1px dashed var(--line);
  border-radius: var(--radius);
}

.viewer-host { flex: 1; display: flex; flex-direction: column; gap: 12px; }

.viewer-toolbar { display: flex; justify-content: space-between; align-items: center; }
.viewer-toolbar h3 { font-family: var(--serif); font-size: 18px; margin: 0; }

.viewer-frame-wrap {
  flex: 1;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--panel);
}

.viewer-frame-wrap iframe { width: 100%; height: 100%; min-height: 60vh; border: none; }

.btn {
  font: inherit;
  font-size: 13px;
  padding: 9px 16px;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: var(--panel);
  cursor: pointer;
}
.btn.ghost { background: none; }
.btn.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
.btn.full { width: 100%; margin-top: 6px; }
.btn.icon { padding: 4px 10px; border: none; font-size: 16px; }

.admin-panel {
  position: fixed;
  inset: 0;
  background: rgba(20, 19, 31, 0.4);
  display: flex;
  justify-content: flex-end;
  z-index: 20;
}

.admin-card {
  width: 340px;
  background: var(--panel);
  height: 100%;
  padding: 24px;
  overflow-y: auto;
}

.admin-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 16px; }
.admin-head h3 { font-family: var(--serif); margin: 0; font-size: 18px; }

.admin-body label { display: block; font-size: 12px; color: var(--muted); margin: 14px 0 6px; }
.admin-body input, .admin-body select {
  width: 100%;
  padding: 9px 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  font: inherit;
  font-size: 13px;
}

.error { color: var(--danger); font-size: 12px; margin-top: 10px; }
.status { font-size: 12px; margin-top: 10px; color: var(--muted); }

a.download-link { color: var(--accent); font-size: 13px; }

@media (max-width: 720px) {
  .layout { grid-template-columns: 1fr; }
  .panel-list { border-right: none; border-bottom: 1px solid var(--line); }
  .admin-card { width: 100%; }
}