:root {
  color-scheme: light dark;
  --theme: light;
  --bg: #f4f6f8;
  --panel: #ffffff;
  --border: #d7dee6;
  --text: #18202a;
  --sub: #576574;
  --accent: #0f766e;
}

[data-theme="dark"] {
  :root {
    --bg: #0b1015;
    --panel: #121a22;
    --border: #2d3946;
    --text: #e6edf3;
    --sub: #9ca9b6;
    --accent: #34d399;
  }
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: radial-gradient(circle at top right, rgba(15,118,110,0.15), transparent 45%), var(--bg);
  color: var(--text);
  font-family: "Segoe UI", "PingFang SC", sans-serif;
}

.layout {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 260px 1fr 280px;
  gap: 12px;
  padding: 12px;
}

.panel {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  padding: 12px;
}

.users-panel ul { list-style: none; padding: 0; margin: 0; }
.users-panel li { padding: 8px; border-bottom: 1px solid var(--border); }
.online-count { color: var(--sub); font-size: 0.7em; font-weight: normal; }

.chat-header { display: flex; justify-content: space-between; align-items: baseline; }
.messages {
  height: calc(100vh - 230px);
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px;
}
.message-item { margin-bottom: 10px; }
.message-meta { color: var(--sub); font-size: 12px; }
.typing { color: var(--sub); min-height: 20px; }

.chat-form {
  margin-top: 10px;
  display: grid;
  grid-template-columns: 1fr 100px;
  gap: 8px;
}

.transfer-controls {
  display: grid;
  gap: 8px;
  margin-bottom: 10px;
}
.transfer-queue {
  border: 1px solid var(--border);
  border-radius: 8px;
  min-height: 120px;
  padding: 8px;
  overflow: auto;
}
.transfer-item {
  border-bottom: 1px solid var(--border);
  padding: 6px 0;
}
.transfer-item:last-child { border-bottom: none; }

.drop-zone {
  position: relative;
  border: 2px dashed var(--border);
  border-radius: 8px;
  padding: 16px 10px;
  text-align: center;
  color: var(--sub);
  font-size: 0.9em;
  cursor: pointer;
  transition: border-color 0.15s, background-color 0.15s;
}
.drop-zone.dragover {
  border-color: var(--accent);
  background: rgba(15, 118, 110, 0.08);
  color: var(--text);
}
.drop-zone input[type="file"] {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
  border: none;
  padding: 0;
}

.file-preview-list {
  list-style: none;
  margin: 0;
  padding: 0;
  max-height: 140px;
  overflow: auto;
}
.file-preview-item {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  padding: 6px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  margin-bottom: 6px;
  font-size: 0.85em;
}
.file-preview-item .file-name {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.file-preview-item .file-size { color: var(--sub); flex-shrink: 0; }
.file-preview-item .file-remove {
  border: none;
  background: transparent;
  color: var(--sub);
  cursor: pointer;
  padding: 0 4px;
  font-size: 1em;
}
.progress {
  height: 8px;
  border-radius: 999px;
  background: rgba(127,127,127,0.2);
  margin-top: 4px;
  overflow: hidden;
}
.progress > span {
  display: block;
  height: 100%;
  background: var(--accent);
}

input, button, select {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px;
  font: inherit;
}
button {
  background: var(--accent);
  color: #fff;
  cursor: pointer;
}

.header-actions { display: flex; gap: 10px; align-items: center; }
.header-btn { height: 40px; padding: 0 12px; border: none; border-radius: 8px; }
.self-label { color: var(--sub); font-size: 0.85em; }

/* 昵称对话框：通过 showModal() 弹出为居中模态，避免 open 属性下渲染进文档流错落到底部 */
#nicknameDialog {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  color: var(--text);
  padding: 20px;
  max-width: 92vw;
}
#nicknameDialog::backdrop { background: rgba(0, 0, 0, 0.45); }
.nickname-form { min-width: 300px; }
.nickname-form input {
  width: 100%;
  margin-top: 8px;
  background: var(--bg);
  color: var(--text);
}
.nickname-actions { display: flex; gap: 8px; margin-top: 8px; }
.error { color: #dc2626; min-height: 20px; }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b1015;
    --panel: #121a22;
    --border: #2d3946;
    --text: #e6edf3;
    --sub: #9ca9b6;
    --accent: #34d399;
  }
}

@media (max-width: 980px) {
  .layout { grid-template-columns: 1fr; }
  .messages { height: 50vh; }
}