/* ============ Paper SPA v1 — 頂 tabs + 左 chat + 右 prod 50/50 + 底 input ============ */

:root {
  --bg:           #1a1a1d;
  --bg-elev:      #232327;
  --bg-elev-2:    #2c2c30;
  --bg-hover:     #34343a;
  --border:       rgba(255, 255, 255, .09);
  --border-soft:  rgba(255, 255, 255, .055);
  --text:         #ececef;
  --text-soft:    #b0b0b6;
  --text-mute:    #6a6a72;
  --accent:       #4a8af0;
  --accent-soft:  rgba(74, 138, 240, .18);
  --accent-text:  #7faaf5;
  --focus-ring:   rgba(74, 138, 240, .35);
  --c-warn:       #ff9f0a;
  --c-ok:         #30d158;
  --font-sans:    Inter, -apple-system, "PingFang TC", "Noto Sans TC", sans-serif;
  --font-serif:   "Noto Serif TC", "Times New Roman", serif;
  --font-mono:    "JetBrains Mono", ui-monospace, monospace;
}

body[data-theme="light"] {
  --bg:           #fafafb;
  --bg-elev:      #ffffff;
  --bg-elev-2:    #f4f4f6;
  --bg-hover:     #ececef;
  --border:       rgba(0, 0, 0, .1);
  --border-soft:  rgba(0, 0, 0, .06);
  --text:         #1d1d1f;
  --text-soft:    #5e5e63;
  --text-mute:    #a0a0a6;
}

* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  height: 100vh;
  overflow: hidden;
  font: 14px/1.5 var(--font-sans);
  background: var(--bg);
  color: var(--text);
}

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

/* ============ Topbar ============ */
.topbar {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 8px 14px;
  background: var(--bg-elev);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  min-height: 50px;
}

.topbar__brand {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}
.topbar__title { font-weight: 700; font-size: 15px; }
.topbar__picker {
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 4px 8px;
  font: 13px var(--font-sans);
  cursor: pointer;
  min-width: 180px;
}

.topbar__tabs {
  display: flex;
  gap: 4px;
  flex: 1 1 auto;
  overflow-x: auto;
  scrollbar-width: thin;
}
.chapter-tab {
  background: transparent;
  color: var(--text-soft);
  border: 1px solid transparent;
  border-radius: 6px 6px 0 0;
  padding: 6px 12px;
  font: 500 13px var(--font-sans);
  cursor: pointer;
  white-space: nowrap;
  transition: background .12s, color .12s;
}
.chapter-tab:hover { background: var(--bg-hover); color: var(--text); }
.chapter-tab.is-active {
  background: var(--bg);
  color: var(--text);
  border-color: var(--border);
  border-bottom-color: var(--bg);
  font-weight: 600;
}

.topbar__actions {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}
.topbar__btn-ghost {
  background: transparent;
  color: var(--text-soft);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 5px 10px;
  font: 500 12.5px var(--font-sans);
  cursor: pointer;
  transition: background .12s, color .12s;
}
.topbar__btn-ghost:hover { background: var(--bg-hover); color: var(--text); }
.topbar__btn-primary {
  background: var(--accent);
  color: #fff;
  border: 1px solid var(--accent);
  border-radius: 6px;
  padding: 5px 12px;
  font: 600 12.5px var(--font-sans);
  cursor: pointer;
}
.topbar__btn-primary:hover { filter: brightness(1.08); }

/* ============ Main split (chat | prod) ============ */
.split {
  display: flex;
  flex: 1 1 auto;
  min-height: 0;
  overflow: hidden;
}
.pane {
  flex: 1 1 50%;
  min-width: 200px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
.pane--chat {
  background: var(--bg-elev);
  border-right: none;
}
.pane--prod {
  background: var(--bg);
}
.split__handle {
  width: 4px;
  background: var(--border);
  cursor: col-resize;
  flex-shrink: 0;
  transition: background .12s;
}
.split__handle:hover,
.split__handle.is-dragging { background: var(--accent); }

/* ============ Chat pane ============ */
.chat-log {
  flex: 1 1 auto;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.chat-empty,
.prod-empty {
  color: var(--text-mute);
  text-align: center;
  padding: 40px 20px;
  font-size: 13.5px;
}
.chat-msg {
  max-width: 92%;
  padding: 10px 14px;
  border-radius: 10px;
  font: 13.5px/1.65 var(--font-sans);
  white-space: pre-wrap;
  word-wrap: break-word;
}
.chat-msg--user {
  align-self: flex-end;
  background: var(--accent-soft);
  color: var(--text);
  border: 1px solid var(--accent);
}
.chat-msg--assistant {
  align-self: flex-start;
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
}
.chat-msg__time {
  font-size: 11px;
  color: var(--text-mute);
  margin-top: 4px;
}

/* ============ Product pane (Word-like) ============ */
.prod-doc {
  flex: 1 1 auto;
  overflow-y: auto;
  padding: 32px max(40px, calc((100% - 720px) / 2)) 60px;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.85 var(--font-serif);
  outline: none;
}
.prod-doc h1 { font: 700 1.8em/1.4 var(--font-serif); margin: 1.5em 0 0.7em; }
.prod-doc h2 { font: 700 1.4em/1.4 var(--font-serif); margin: 1.3em 0 0.6em; border-bottom: 1px solid var(--border-soft); padding-bottom: 0.2em; }
.prod-doc h3 { font: 600 1.18em/1.4 var(--font-serif); margin: 1.1em 0 0.5em; }
.prod-doc h4 { font: 600 1.05em/1.4 var(--font-serif); margin: 1em 0 0.4em; color: var(--text-soft); }
.prod-doc p { margin: 0 0 0.9em; text-indent: 2em; }
.prod-doc p.no-indent,
.prod-doc blockquote p { text-indent: 0; }
.prod-doc ul, .prod-doc ol { margin: 0 0 1em; padding-left: 2em; }
.prod-doc li { margin: 0.2em 0; }
.prod-doc strong { font-weight: 700; color: var(--text); }
.prod-doc em { font-style: italic; }
.prod-doc a { color: var(--accent); text-decoration: none; border-bottom: 1px dashed currentColor; }
.prod-doc blockquote {
  border-left: 3px solid var(--accent);
  padding: 6px 16px;
  margin: 1em 0;
  background: var(--bg-elev-2);
  color: var(--text-soft);
}
.prod-doc table { border-collapse: collapse; margin: 1em 0; width: 100%; }
.prod-doc th, .prod-doc td { border: 1px solid var(--border); padding: 6px 10px; }
.prod-doc th { background: var(--bg-elev); font-weight: 600; }
.prod-doc img { max-width: 100%; height: auto; margin: 0.5em 0; }
.prod-doc code { background: var(--bg-elev-2); padding: 1px 5px; border-radius: 3px; font: 0.9em var(--font-mono); }
.prod-doc pre { background: var(--bg-elev-2); padding: 12px; border-radius: 6px; overflow-x: auto; }
.prod-doc[contenteditable="true"] { outline: 1px dashed var(--accent); outline-offset: -2px; }

/* ============ Bottom input bar ============ */
.inputbar {
  display: flex;
  align-items: flex-end;
  gap: 8px;
  padding: 10px 14px;
  background: var(--bg-elev);
  border-top: 1px solid var(--border);
  flex-shrink: 0;
}
.inputbar__attach {
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 12px;
  font-size: 16px;
  cursor: pointer;
  flex-shrink: 0;
}
.inputbar__attach:hover { background: var(--bg-hover); }
.inputbar__textarea {
  flex: 1 1 auto;
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 14px;
  font: 13.5px/1.5 var(--font-sans);
  resize: none;
  outline: none;
  max-height: 200px;
  min-height: 38px;
}
.inputbar__textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 2px var(--focus-ring); }
.inputbar__send {
  background: var(--accent);
  color: #fff;
  border: 1px solid var(--accent);
  border-radius: 8px;
  padding: 8px 18px;
  font: 600 13px var(--font-sans);
  cursor: pointer;
  flex-shrink: 0;
}
.inputbar__send:hover { filter: brightness(1.08); }
.inputbar__send:disabled { opacity: 0.5; cursor: not-allowed; }

/* ============ Modal ============ */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 100;
}
.modal:not([hidden]) { display: flex; }
.modal__panel {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 20px;
  min-width: 360px;
  max-width: 500px;
}
.modal__head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 12px; }
.modal__head h3 { margin: 0; font-size: 16px; font-weight: 600; }
.modal__close {
  background: transparent;
  border: 0;
  color: var(--text-soft);
  font-size: 22px;
  cursor: pointer;
  padding: 0 6px;
}
.modal__body { margin: 8px 0 16px; }
.modal__body label { display: block; font-size: 13px; color: var(--text-soft); margin-bottom: 4px; }
.modal__body input {
  width: 100%;
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
  font: 13.5px var(--font-sans);
  outline: none;
}
.modal__body input:focus { border-color: var(--accent); }
.modal__hint { font-size: 12px; color: var(--text-mute); margin: 8px 0 0; line-height: 1.5; }
.modal__actions { display: flex; gap: 8px; justify-content: flex-end; }
.modal__btn {
  background: transparent;
  color: var(--text-soft);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 14px;
  font: 500 13px var(--font-sans);
  cursor: pointer;
}
.modal__btn:hover { background: var(--bg-hover); color: var(--text); }
.modal__btn--primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  font-weight: 600;
}
.modal__btn--primary:hover { filter: brightness(1.08); }

/* ============ Toast ============ */
.toast {
  position: fixed;
  bottom: 90px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 18px;
  font: 500 13px var(--font-sans);
  box-shadow: 0 4px 16px rgba(0, 0, 0, .3);
  z-index: 200;
  animation: toast-in .2s ease-out;
}
.toast[hidden] { display: none; }
@keyframes toast-in {
  from { transform: translate(-50%, 10px); opacity: 0; }
  to { transform: translate(-50%, 0); opacity: 1; }
}