:root {
  --bg: #0f1419;
  --bg-elevated: #1a222d;
  --border: #2d3a47;
  --text: #e8eef4;
  --text-muted: #8fa3b0;
  --accent: #3d9cf0;
  --accent-hover: #5cb0f5;
  --success: #4ade80;
  --error: #f87171;
  --radius: 12px;
  --font-ui: "IBM Plex Sans", system-ui, sans-serif;
  --font-thai: "Noto Sans Thai", var(--font-ui);
  --font-lao: "Noto Sans Lao", var(--font-ui);
  --font-zh: "Noto Sans SC", var(--font-ui);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-ui);
  background: radial-gradient(ellipse 120% 80% at 50% -20%, #1e3a5f 0%, transparent 55%),
    var(--bg);
  color: var(--text);
  line-height: 1.5;
}

.app {
  max-width: 960px;
  margin: 0 auto;
  padding: 2rem 1.25rem 3rem;
}

.header {
  margin-bottom: 2rem;
}

.header__brand {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
}

.header__logo {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: 14px;
  background: linear-gradient(145deg, var(--accent), #2563ab);
  font-size: 1.25rem;
  color: #fff;
  flex-shrink: 0;
}

.header__title {
  margin: 0;
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.header__subtitle {
  margin: 0.35rem 0 0;
  font-size: 0.95rem;
  color: var(--text-muted);
}

.main {
  display: grid;
  gap: 1.25rem;
}

@media (min-width: 800px) {
  .main {
    grid-template-columns: 1fr 1fr;
    align-items: stretch;
  }
}

.panel {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.1rem 1.1rem;
  display: flex;
  flex-direction: column;
  min-height: 320px;
}

.panel__head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 0.75rem;
  margin-bottom: 0.75rem;
}

.panel__label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-right: auto;
}

.select {
  appearance: none;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.45rem 2rem 0.45rem 0.75rem;
  border-radius: 8px;
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%238fa3b0' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.6rem center;
  min-width: 140px;
}

.select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.textarea {
  flex: 1;
  width: 100%;
  min-height: 180px;
  resize: vertical;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  padding: 0.85rem 1rem;
  font-family: inherit;
  font-size: 1rem;
  line-height: 1.55;
}

.textarea:focus {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.textarea.lang-th {
  font-family: var(--font-thai);
}

.textarea.lang-lo {
  font-family: var(--font-lao);
}

.textarea.lang-zh {
  font-family: var(--font-zh);
}

.output {
  flex: 1;
  min-height: 180px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.85rem 1rem;
  font-size: 1rem;
  line-height: 1.55;
  white-space: pre-wrap;
  word-break: break-word;
}

.output.lang-th {
  font-family: var(--font-thai);
}

.output.lang-lo {
  font-family: var(--font-lao);
}

.output.lang-zh {
  font-family: var(--font-zh);
}

.output:empty::before {
  content: "Bản dịch sẽ hiển thị ở đây…";
  color: var(--text-muted);
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.85rem;
}

.hint {
  font-size: 0.85rem;
  color: var(--text-muted);
  flex: 1;
  min-width: 0;
}

.hint--error {
  color: var(--error);
}

.hint--ok {
  color: var(--success);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  padding: 0.55rem 1rem;
  border-radius: 8px;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: background 0.15s ease, transform 0.1s ease;
}

.btn:active {
  transform: scale(0.98);
}

.btn--primary {
  background: var(--accent);
  color: #fff;
}

.btn--primary:hover {
  background: var(--accent-hover);
}

.btn--secondary {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}

.btn--secondary:hover {
  background: rgba(255, 255, 255, 0.06);
}

.btn--ghost {
  background: transparent;
  color: var(--accent);
  border: 1px solid transparent;
  padding: 0.4rem 0.65rem;
  font-size: 0.85rem;
  font-weight: 500;
}

.btn--ghost:hover {
  background: rgba(61, 156, 240, 0.12);
  border-color: rgba(61, 156, 240, 0.35);
}

.btn__icon {
  font-size: 0.7rem;
  opacity: 0.9;
}

.footer {
  margin-top: 2rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
}

.footer p {
  margin: 0;
  font-size: 0.8rem;
  color: var(--text-muted);
  max-width: 52ch;
}