:root {
  --bg: #f4f6f8;
  --surface: #ffffff;
  --border: #e1e5ea;
  --text: #1f2a37;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-contrast: #ffffff;
  --user-bubble: #2563eb;
  --assistant-bubble: #eef1f5;
  --radius: 10px;
  font-family:
    system-ui,
    -apple-system,
    Segoe UI,
    Roboto,
    sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
}

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  max-width: 820px;
  margin: 0 auto;
  background: var(--surface);
}

.app__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
}

.app__brand {
  font-weight: 600;
  font-size: 16px;
}

.app__tabs {
  display: flex;
  gap: 4px;
}

.tab {
  border: none;
  background: transparent;
  color: var(--muted);
  padding: 6px 12px;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 14px;
}

.tab--active {
  background: var(--assistant-bubble);
  color: var(--text);
  font-weight: 600;
}

.view {
  display: none;
  flex: 1;
  min-height: 0;
  flex-direction: column;
}

.view--active {
  display: flex;
}

.messages {
  flex: 1;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.empty {
  color: var(--muted);
  text-align: center;
  margin: auto;
  max-width: 420px;
  line-height: 1.5;
}

.msg {
  max-width: 78%;
  padding: 10px 12px;
  border-radius: var(--radius);
  line-height: 1.45;
  white-space: pre-wrap;
  word-wrap: break-word;
}

.msg--user {
  align-self: flex-end;
  background: var(--user-bubble);
  color: var(--accent-contrast);
}

.msg--assistant {
  align-self: flex-start;
  background: var(--assistant-bubble);
  color: var(--text);
}

.msg--error {
  align-self: center;
  background: #fde8e8;
  color: #9b1c1c;
  font-size: 13px;
}

.composer {
  display: flex;
  gap: 8px;
  padding: 12px 16px;
  border-top: 1px solid var(--border);
}

.composer__input {
  flex: 1;
  resize: none;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px 12px;
  font: inherit;
}

.composer__send,
.settings__save {
  border: none;
  background: var(--accent);
  color: var(--accent-contrast);
  padding: 0 18px;
  border-radius: var(--radius);
  cursor: pointer;
  font: inherit;
  font-weight: 600;
}

.composer__send:disabled,
.settings__save:disabled {
  opacity: 0.6;
  cursor: default;
}

.settings {
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  max-width: 460px;
}

.settings__title {
  margin: 0;
  font-size: 16px;
}

.settings__hint,
.settings__feedback {
  margin: 0;
  font-size: 13px;
  color: var(--muted);
}

.settings__feedback--ok {
  color: #047857;
}

.settings__feedback--err {
  color: #9b1c1c;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.field__label {
  font-size: 13px;
  color: var(--muted);
}

.field__control {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px 12px;
  font: inherit;
  background: var(--surface);
}

.settings__save {
  padding: 10px 18px;
  align-self: flex-start;
}