:root {
  /* 默认使用浅色主题变量 */
  --bg: #f6f8fb;
  --card: rgba(0, 0, 0, 0.02);
  --border: rgba(0, 0, 0, 0.08);
  --text: #1a1f2a;
  --muted: #5b6372;
  --brand: #ff7a59; /* 更柔和的珊瑚橙 */
  --brand-2: #ffd59e; /* 粉杏辅助 */
  --accent: #2ec8a3;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, "Helvetica Neue", Arial, "Noto Sans", "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  /* 默认浅色背景：柔和浅杏+淡蓝过渡 */
  background: radial-gradient(1000px 500px at 10% -10%, #fff6eb, transparent),
              radial-gradient(800px 500px at 120% 20%, #eef4ff, transparent),
              var(--bg);
}

.app { min-height: 100dvh; display: grid; grid-template-rows: auto auto 1fr auto; }

/* Header */
.app-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: 16px 16px; backdrop-filter: saturate(1.2) blur(12px);
  background: linear-gradient(180deg, rgba(255,255,255,0.75), rgba(255,255,255,0.35));
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
  box-shadow: 0 8px 24px rgba(0,0,0,0.06);
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand-icon { font-size: 24px; filter: drop-shadow(0 1px 0 rgba(0,0,0,0.15)); }
.brand-text h1 { margin: 0; font-size: 18px; letter-spacing: 0.2px; }
.brand-text .subtitle { margin: 2px 0 0; color: var(--muted); font-size: 12px; }
.header-actions { display: flex; align-items: center; gap: 8px; }
.tag {
  padding: 6px 10px; border-radius: 999px; font-size: 12px; color: #161a1f;
  background: linear-gradient(90deg, var(--brand), var(--brand-2));
}
.icon-btn {
  border: 1px solid var(--border); background: var(--card); color: var(--text);
  border-radius: 10px; padding: 6px 10px; cursor: pointer; transition: all .2s ease;
}
.icon-btn:hover { transform: translateY(-1px); background: rgba(255,255,255,0.1); }

/* Quick prompts */
.quick-prompts {
  display: grid; grid-auto-flow: column; grid-auto-columns: max-content; gap: 8px;
  padding: 12px 16px; overflow-x: auto; scrollbar-width: none; -ms-overflow-style: none;
}
.quick-prompts::-webkit-scrollbar { display: none; }
.chip {
  font-size: 13px; color: var(--text); border: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(255,255,255,0.06), rgba(255,255,255,0.02));
  border-radius: 999px; padding: 8px 12px; cursor: pointer; white-space: nowrap; transition: all .2s;
}
.chip:hover { border-color: rgba(255,255,255,0.18); transform: translateY(-1px); }

/* Chat */
.chat {
  display: flex; flex-direction: column; gap: 14px;
  /* 增加底部留白，避免消息贴近输入框，考虑安全区 */
  padding: 14px 14px calc(140px + env(safe-area-inset-bottom));
}
.bubble {
  display: grid; grid-template-columns: 34px 1fr; gap: 12px; align-items: start;
}
.bubble.ai { align-self: flex-start; grid-template-columns: 34px 1fr; }
.bubble.user { align-self: flex-end; grid-template-columns: 1fr 34px; }
.avatar { width: 34px; height: 34px; border-radius: 10px; display: grid; place-items: center; font-size: 18px; box-shadow: 0 3px 8px rgba(0,0,0,0.08); }
.avatar.ai { background: rgba(63, 215, 183, 0.18); border: 1px solid rgba(63,215,183,0.35); }
.avatar.user { background: rgba(255, 200, 150, 0.18); border: 1px solid rgba(255, 180, 120, 0.35); }
.msg {
  border: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(255,255,255,0.85), rgba(255,255,255,0.65));
  border-radius: 18px; padding: 12px 15px; line-height: 1.65; font-size: 15px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.06), inset 0 1px 0 rgba(255,255,255,0.6);
}
.msg .meta { color: var(--muted); font-size: 12px; margin-bottom: 6px; }
.msg .content { white-space: pre-wrap; word-break: break-word; }

/* 标题与分隔线（用于轻量 Markdown 渲染） */
.msg .content .h1 { font-size: 16px; font-weight: 800; margin: 8px 0 4px; color: var(--text); letter-spacing: .2px; }
.msg .content .h2 { font-size: 15px; font-weight: 700; margin: 8px 0 4px; color: var(--text); border-left: 3px solid var(--brand); padding-left: 8px; }
.msg .content .h3 { font-size: 14px; font-weight: 600; margin: 6px 0 2px; color: var(--text); opacity: .92; }
.msg .content .divider { border: none; border-top: 1px dashed var(--border); margin: 8px 0; }

.msg.ai { border-color: rgba(46,200,163,0.45); box-shadow: 0 10px 24px rgba(46,200,163,0.18), inset 0 1px 0 rgba(255,255,255,0.6); }
.msg.user { border-color: rgba(255, 150, 100, 0.45); box-shadow: 0 10px 24px rgba(255,150,100,0.18), inset 0 1px 0 rgba(255,255,255,0.6); }

.thinking {
  display: inline-flex; align-items: center; gap: 6px; color: var(--muted); font-size: 13px;
}
.dot { width: 6px; height: 6px; border-radius: 999px; background: var(--muted); opacity: 0.6; animation: pulse 1.2s infinite ease-in-out; }
.dot:nth-child(2) { animation-delay: .15s; }
.dot:nth-child(3) { animation-delay: .3s; }
@keyframes pulse { 0%, 80%, 100% { transform: scale(.8); opacity: .4; } 40% { transform: scale(1); opacity: .9; } }

/* Composer */
.composer {
  position: fixed; bottom: 0; left: 0; right: 0; padding: 12px 12px 16px; backdrop-filter: blur(12px) saturate(1.1);
  background: linear-gradient(180deg, rgba(255,255,255,0.65), rgba(255,255,255,0.85));
  border-top: 1px solid var(--border);
  box-shadow: 0 -10px 24px rgba(0,0,0,0.06);
}
.composer-inner {
  display: grid; grid-template-columns: 1fr auto; gap: 8px; align-items: stretch;
}
.input {
  resize: none; width: 100%; border: 1px solid var(--border); border-radius: 16px; padding: 12px 12px 12px 12px;
  background: rgba(255,255,255,0.85); color: var(--text); font-size: 15px; line-height: 1.6;
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.6);
}
.input:focus { outline: none; border-color: var(--brand); box-shadow: 0 0 0 3px rgba(255,122,89,0.25), inset 0 1px 0 rgba(255,255,255,0.7); }
.send-btn {
  position: relative; overflow: hidden; display: inline-flex; align-items: center; justify-content: center;
  border: none; border-radius: 16px; padding: 0 22px; min-width: 88px; height: 100%; font-weight: 700; cursor: pointer; color: #161a1f;
  background: linear-gradient(90deg, var(--brand), var(--brand-2)); box-shadow: 0 8px 18px rgba(255, 130, 67, 0.28);
}
.send-btn:active { transform: translateY(1px) scale(0.98); box-shadow: 0 6px 14px rgba(255, 130, 67, 0.26); }
.send-btn::before {
  content: ""; position: absolute; top: 0; bottom: 0; left: -40%; width: 40%;
  background: linear-gradient(90deg, rgba(255,255,255,0.0), rgba(255,255,255,0.45), rgba(255,255,255,0.0));
  transform: skewX(-20deg); opacity: 0;
}
.send-btn:hover::before { animation: sheen 1200ms ease-in-out; }
.hint { margin-top: 8px; color: var(--muted); font-size: 12px; }

/* Quick prompts with impact */
.chip {
  position: relative; overflow: hidden;
  font-size: 13px; color: var(--text); border: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(255,255,255,0.85), rgba(255,255,255,0.55));
  border-radius: 999px; padding: 9px 13px; cursor: pointer; white-space: nowrap; transition: transform .15s ease, box-shadow .15s ease;
  box-shadow: 0 4px 14px rgba(0,0,0,0.05);
}
.chip:hover { border-color: rgba(0,0,0,0.16); transform: translateY(-1px) scale(1.02); box-shadow: 0 6px 18px rgba(0,0,0,0.06); }
.chip:active { transform: scale(0.98); }

/* Ripple effect */
.ripple {
  position: absolute; border-radius: 50%; pointer-events: none;
  width: var(--ripple-size, 120px); height: var(--ripple-size, 120px);
  left: var(--ripple-x, 50%); top: var(--ripple-y, 50%);
  transform: translate(-50%, -50%);
  background: radial-gradient(circle, rgba(255,255,255,0.35) 0%, rgba(255,255,255,0.25) 40%, transparent 70%);
  animation: ripple 600ms ease-out forwards;
}
@keyframes ripple { from { opacity: .8; transform: translate(-50%, -50%) scale(.6); } to { opacity: 0; transform: translate(-50%, -50%) scale(2.4); } }

/* Bubble entrance animations */
.bubble.ai { animation: popInLeft 220ms ease-out; }
.bubble.user { animation: popInRight 220ms ease-out; }
@keyframes popInLeft { from { opacity: 0; transform: translateX(-10px) scale(.98); } to { opacity: 1; transform: translateX(0) scale(1); } }
@keyframes popInRight { from { opacity: 0; transform: translateX(10px) scale(.98); } to { opacity: 1; transform: translateX(0) scale(1); } }

@keyframes sheen { from { left: -40%; opacity: 0; } 25% { opacity: .6; } to { left: 140%; opacity: 0; } }
.hint { margin-top: 8px; color: var(--muted); font-size: 12px; }

/* Responsive tweaks */
@media (min-width: 640px) {
  .app { max-width: 720px; margin: 0 auto; }
  .quick-prompts { justify-content: start; }
}

/* Dark theme（可选，切换时应用）*/
.dark {
  --bg: #0b0f14;
  --card: rgba(255, 255, 255, 0.06);
  --border: rgba(255, 255, 255, 0.09);
  --text: #e7eaf0;
  --muted: #a7b0c0;
}

/* Dark 背景覆盖 */
.dark body {
  background: radial-gradient(1200px 600px at 20% -10%, #17202c, transparent),
              radial-gradient(900px 600px at 120% 20%, #1c1f24, transparent),
              var(--bg);
}

/* Dark 组件对比度优化 */
.dark .app-header {
  background: linear-gradient(180deg, rgba(24,28,34,0.85), rgba(24,28,34,0.65));
  border-bottom-color: rgba(255,255,255,0.08);
}
.dark .icon-btn { border-color: rgba(255,255,255,0.12); background: rgba(255,255,255,0.06); color: var(--text); }
.dark .chip {
  border-color: rgba(255,255,255,0.12);
  background: linear-gradient(180deg, rgba(255,255,255,0.06), rgba(255,255,255,0.03));
}
.dark .bubble .msg {
  border-color: rgba(255,255,255,0.12);
  background: linear-gradient(180deg, rgba(22,26,32,0.92), rgba(22,26,32,0.78));
  box-shadow: 0 8px 20px rgba(0,0,0,0.35), inset 0 1px 0 rgba(255,255,255,0.08);
}
.dark .avatar.ai { background: rgba(46, 200, 163, 0.22); border-color: rgba(46,200,163,0.45); }
.dark .avatar.user { background: rgba(255, 180, 120, 0.22); border-color: rgba(255,180,120,0.45); }
.dark .thinking { color: var(--muted); }
.dark .dot { background: var(--muted); opacity: 0.75; }
.dark .composer {
  backdrop-filter: blur(12px) saturate(1.1);
  background: linear-gradient(180deg, rgba(20,24,30,0.85), rgba(20,24,30,0.95));
  border-top-color: rgba(255,255,255,0.08);
}
.dark .input {
  border-color: rgba(255,255,255,0.12);
  background: rgba(16,20,26,0.85);
  color: var(--text);
}
.dark .send-btn { box-shadow: 0 8px 18px rgba(255,130,67,0.22); }