:root {
  color-scheme: light;
  --ink: #17252b;
  --muted: #63747a;
  --line: #dce5e2;
  --paper: #f8faf7;
  --panel: #ffffff;
  --accent: #0c756d;
  --accent-soft: #dff0e9;
  --warm: #c86f3d;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  background: var(--paper);
  font-family: Georgia, "Noto Serif SC", serif;
}

button, textarea, select { font: inherit; }

button { cursor: pointer; }

.chat-shell {
  display: grid;
  grid-template-columns: minmax(230px, 285px) minmax(0, 1fr);
  min-height: 100vh;
  max-width: 1440px;
  margin: 0 auto;
  background: var(--panel);
}

.conversation-panel {
  display: flex;
  flex-direction: column;
  padding: 30px 20px;
  border-right: 1px solid var(--line);
  background: #eef5ef;
}

.panel-heading, .chat-heading, .composer-tools, .composer-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.eyebrow {
  margin: 0 0 7px;
  color: var(--accent);
  font-family: Arial, sans-serif;
  font-size: 10px;
  font-weight: 700;
  letter-spacing: .16em;
}

h1, h2, h3, p { margin-top: 0; }
h1 { margin-bottom: 0; font-size: 23px; }
h2 { margin-bottom: 0; font-size: clamp(22px, 3vw, 34px); }

.new-conversation-button {
  width: 100%;
  min-height: 46px;
  margin-top: 20px;
  padding: 12px 16px;
  border: 1px solid var(--accent);
  border-radius: 8px;
  color: #fff;
  background: var(--accent);
  font-size: 16px;
  font-weight: 700;
}

.new-conversation-button:hover { background: #095c56; }
.message-content a.lecture-reference,
.message-content a.lecture-reference:visited,
.empty-state a.lecture-reference,
.empty-state a.lecture-reference:visited { color: #1565c0; text-decoration: underline; text-underline-offset: 3px; }
.message-content a.lecture-reference:hover,
.empty-state a.lecture-reference:hover { color: #003c8f; }
.message-content a.lecture-reference:focus-visible,
.empty-state a.lecture-reference:focus-visible { outline: 2px solid #1565c0; outline-offset: 3px; }
.chat-shell[hidden], .lecture-reader[hidden] { display: none; }
body.pdf-reading { overflow: hidden; }
.answer-diagram { display: block; text-align: center; }
.diagram-output { display: flex; overflow-x: auto; padding: 12px; min-height: 70px; font: 13px Arial, sans-serif; color: var(--muted); }
.diagram-svg { display: block; flex: none; margin: 0 auto; overflow: visible; }
.diagram-toggle { padding: 4px 9px; border: 1px solid var(--line); border-radius: 6px; background: #fff; color: var(--muted); font: 12px Arial, sans-serif; }
.diagram-source { display: block; text-align: left; white-space: pre-wrap; overflow-wrap: anywhere; padding: 10px; font-size: 12px; }
.diagram-source[hidden] { display: none; }
[data-diagram-state="error"] .diagram-output { color: #8d3e25; }
.lecture-reader { position: fixed; inset: 0; z-index: 1000; display: flex; flex-direction: column; background: #d9dee2; }
.pdf-toolbar { flex: none; display: flex; align-items: center; flex-wrap: wrap; gap: 10px; padding: 10px 16px; background: #fff; border-bottom: 1px solid var(--line); font-family: Arial, sans-serif; }
.pdf-toolbar button, .pdf-toolbar select { padding: 9px 12px; border: 1px solid #b8c9c4; border-radius: 6px; background: #fff; color: var(--ink); font: inherit; font-size: 14px; }
.pdf-toolbar .pdf-return { background: var(--accent); color: white; border-color: var(--accent); font-weight: 700; }
.pdf-toolbar button:disabled, .pdf-toolbar select:disabled { opacity: .45; cursor: default; }
.pdf-controls { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; }
#pdf-title { font-weight: 700; }
#pdf-page-label { margin-left: auto; white-space: nowrap; font-size: 13px; }
.pdf-status { flex: none; margin: 0; padding: 9px 16px; background: #fff8e9; font: 14px Arial, sans-serif; }
.pdf-status[hidden] { display: none; }
.pdf-status.error { color: #902e21; }
.pdf-stage { position: relative; flex: 1; min-height: 0; }
#pdf-scroll { position: absolute; inset: 0; overflow-x: auto; overflow-y: scroll; scrollbar-gutter: stable; overscroll-behavior: contain; }
#pdf-scroll .pdfViewer { min-height: 100%; }
@media (max-width: 600px) {
  .pdf-toolbar { padding: 8px; gap: 7px; }
  .pdf-controls { width: 100%; order: 3; gap: 5px; }
  .pdf-toolbar button, .pdf-toolbar select { padding: 8px; font-size: 13px; }
  #pdf-title { font-size: 13px; }
}
.new-conversation-button:focus-visible { outline: 3px solid var(--warm); outline-offset: 3px; }
.conversation-row { display: flex; align-items: center; gap: 5px; min-width: 0; }
.conversation-row .conversation-item { flex: 1; min-width: 0; }
.delete-conversation { flex-shrink: 0; padding: 8px 6px; border: 1px solid var(--line); border-radius: 6px; color: #944022; background: var(--panel); font-size: 12px; }
.delete-conversation:disabled { opacity: .5; cursor: wait; }
.chat-notice { margin: 16px clamp(20px, 5vw, 72px) 0; padding: 12px 15px; border-left: 4px solid var(--warm); background: #fff6e9; color: #704820; font-family: Arial, sans-serif; font-size: 14px; line-height: 1.6; }
.chat-notice[hidden] { display: none; }
.chat-notice.error { color: #902e21; background: #fff0ed; border-color: #b64c39; }

.conversation-list {
  display: grid;
  gap: 7px;
  margin-top: 31px;
  overflow-y: auto;
}

.conversation-item {
  display: block;
  width: 100%;
  padding: 12px 11px;
  border: 1px solid transparent;
  border-radius: 8px;
  color: var(--ink);
  background: transparent;
  text-align: left;
}

.conversation-item:hover, .conversation-item.active {
  border-color: #b8d6ca;
  background: var(--panel);
}

.conversation-title {
  display: block;
  overflow: hidden;
  font-size: 14px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.conversation-date {
  display: block;
  margin-top: 5px;
  color: var(--muted);
  font-family: Arial, sans-serif;
  font-size: 10px;
}

.panel-note {
  margin: auto 0 0;
  padding-top: 24px;
  color: var(--muted);
  font-family: Arial, sans-serif;
  font-size: 11px;
  line-height: 1.65;
}

.chat-panel {
  display: flex;
  flex-direction: column;
  min-width: 0;
  min-height: 100vh;
}

.chat-heading {
  padding: 30px clamp(20px, 5vw, 72px) 24px;
  border-bottom: 1px solid var(--line);
}

.chat-heading-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; }

.history-more { margin: 12px auto; padding: 8px 14px; border: 1px solid var(--line); border-radius: 8px; background: white; color: var(--accent); font: 13px Arial, sans-serif; cursor: pointer; }
.history-more:disabled { opacity: .5; cursor: wait; }
.history-more[hidden] { display: none; }

.teacher-link {
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: #fff;
  font-family: Arial, sans-serif;
  font-size: 10px;
  text-decoration: none;
}

.teacher-link:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }

.logout-button {
  padding: 7px 10px;
  border: 1px solid #e7b6a3;
  border-radius: 999px;
  color: #9b4025;
  background: #fff6f1;
  font-family: Arial, sans-serif;
  font-size: 10px;
}

.logout-button:hover { border-color: var(--warm); color: #7d321e; background: #fbe9df; }
.logout-button:disabled { cursor: wait; opacity: .55; }

.status-pill {
  padding: 7px 10px;
  border-radius: 100px;
  color: var(--accent);
  background: var(--accent-soft);
  font-family: Arial, sans-serif;
  font-size: 11px;
}

.message-list {
  display: flex;
  flex: 1;
  flex-direction: column;
  gap: 20px;
  width: min(900px, 100%);
  margin: 0 auto;
  padding: 44px clamp(20px, 5vw, 72px);
  overflow-y: auto;
}

.empty-state {
  max-width: 480px;
  margin: auto;
  color: var(--muted);
  text-align: center;
}

.empty-mark {
  display: block;
  margin-bottom: 16px;
  color: var(--warm);
  font-size: 34px;
}

.empty-state h3 { margin-bottom: 8px; color: var(--ink); font-size: 22px; }
.empty-state p { font-family: Arial, sans-serif; font-size: 13px; line-height: 1.8; }
.empty-state p + p { margin-top: 12px; }
.welcome-example a { margin: 0 .25em; }

.message {
  max-width: 85%;
  padding: 15px 17px;
  border-radius: 12px;
  line-height: 1.7;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

.message.user {
  align-self: flex-end;
  color: #fff;
  background: var(--accent);
}

.message.assistant {
  align-self: flex-start;
  border: 1px solid var(--line);
  background: #fff;
}

.message.assistant .message-content { white-space: normal; }
.message-content > :first-child { margin-top: 0; }
.message-content > :last-child { margin-bottom: 0; }
.message-content p { margin: 0 0 .85em; }
.message-content h1, .message-content h2, .message-content h3,
.message-content h4, .message-content h5, .message-content h6 {
  margin: 1.15em 0 .5em;
  color: var(--ink);
  font-size: 1.12em;
  line-height: 1.5;
}
.message-content h1 { font-size: 1.35em; }
.message-content h2 { font-size: 1.22em; }
.message-content blockquote {
  margin: .9em 0;
  padding: .7em 1em;
  border-left: 3px solid var(--accent);
  border-radius: 0 6px 6px 0;
  background: var(--accent-soft);
}
.message-content blockquote > :last-child { margin-bottom: 0; }
.message-content ul, .message-content ol { margin: .5em 0 1em; padding-left: 1.6em; }
.message-content li + li { margin-top: .3em; }
.message-content li > p { margin-bottom: .35em; }
.message-content hr { margin: 1.3em 0; border: 0; border-top: 1px solid var(--line); }
.message-content pre {
  max-width: 100%;
  overflow-x: auto;
  padding: .8em 1em;
  border-radius: 6px;
  background: var(--paper);
  white-space: pre;
}
.message-content code { font-family: ui-monospace, monospace; font-size: .88em; }
.message-content :not(pre) > code { padding: .1em .25em; background: var(--paper); }
.message-content table { display: block; max-width: 100%; overflow-x: auto; border-collapse: collapse; margin: .8em 0; }
.message-content th, .message-content td { padding: .35em .65em; border: 1px solid var(--line); }
.message-content a { color: var(--accent); text-underline-offset: .2em; }
.answer-math-display { display: block; max-width: 100%; overflow-x: auto; overflow-y: hidden; }
.answer-math .katex-display { margin: .65em 0; }
.math-error { white-space: pre-wrap; }

.message-content .katex-display {
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 3px 0;
}

.message-content .katex {
  font-size: 1.05em;
}

.feedback-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 12px;
  padding-top: 9px;
  border-top: 1px solid var(--line);
}

.feedback-actions button {
  padding: 4px 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: #fff;
  font-family: Arial, sans-serif;
  font-size: 10px;
}

.feedback-actions button:hover,
.feedback-actions button.selected {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-soft);
}

.composer {
  width: min(900px, 100%);
  margin: 0 auto;
  padding: 0 clamp(20px, 5vw, 72px) 28px;
}

.composer-tools {
  justify-content: flex-start;
  margin-bottom: 8px;
  color: var(--muted);
  font-family: Arial, sans-serif;
  font-size: 11px;
}

.composer-tools select {
  padding: 5px 8px;
  border: 1px solid var(--line);
  border-radius: 5px;
  color: var(--ink);
  background: #fff;
  font-size: 12px;
}

.input-count { margin-left: auto; }

textarea {
  display: block;
  width: 100%;
  resize: vertical;
  padding: 14px;
  border: 1px solid #b8c9c4;
  border-radius: 9px;
  outline: none;
  color: var(--ink);
  background: #fff;
  line-height: 1.6;
}

textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }

.composer-footer { margin-top: 9px; }
.composer-footer p { margin-bottom: 0; color: var(--muted); font-family: Arial, sans-serif; font-size: 10px; }
.composer-footer #daily-budget { font-size: 12px; }
#budget-remaining { font-variant-numeric: tabular-nums; font-weight: 600; }

.composer-actions { display: flex; gap: 8px; }

.send-button {
  padding: 10px 18px;
  border: 0;
  border-radius: 6px;
  color: #fff;
  background: var(--accent);
  font-family: Arial, sans-serif;
  font-size: 12px;
  font-weight: 700;
}

.send-button:disabled { cursor: wait; opacity: .55; }

.stop-button {
  padding: 10px 14px;
  border: 1px solid #c86f3d;
  border-radius: 6px;
  color: #9b4025;
  background: #fff6f1;
  font-family: Arial, sans-serif;
  font-size: 12px;
  font-weight: 700;
}

.stop-button:disabled { cursor: wait; opacity: .55; }

.error-message { border-color: #e7b6a3; color: #8d3e25; background: #fff6f1; }

.login-page {
  min-height: 100vh;
  background:
    radial-gradient(circle at 18% 16%, rgba(200, 111, 61, .2), transparent 28rem),
    linear-gradient(135deg, #e7f0e8 0%, #f7f3e9 52%, #e8efeb 100%);
}

.login-shell {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(360px, .95fr);
  min-height: 100vh;
}

.login-intro {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: clamp(48px, 9vw, 132px);
  border-right: 1px solid rgba(23, 37, 43, .12);
}

.login-intro h1 {
  max-width: 8em;
  font-size: clamp(48px, 7vw, 92px);
  font-weight: 500;
  line-height: .98;
  letter-spacing: -.045em;
}

.login-lead {
  max-width: 31em;
  margin: 34px 0 0;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.9;
}

.algebra-mark {
  display: flex;
  align-items: baseline;
  gap: 18px;
  margin-top: 56px;
  color: var(--accent);
  font-size: clamp(32px, 5vw, 64px);
}

.algebra-mark i { color: var(--warm); font-size: .7em; font-style: normal; }
.algebra-mark sub { font-size: .45em; }

.login-panel {
  display: grid;
  place-items: center;
  padding: 32px;
}

.login-card {
  width: min(430px, 100%);
  padding: clamp(30px, 5vw, 56px);
  border: 1px solid rgba(23, 37, 43, .12);
  border-radius: 3px 28px 3px 3px;
  background: rgba(255, 255, 255, .86);
  box-shadow: 0 26px 70px rgba(40, 57, 52, .12);
  backdrop-filter: blur(14px);
}

.login-card h2 { font-size: 31px; }
.login-note { margin: 12px 0 30px; color: var(--muted); font-size: 13px; line-height: 1.7; }
.login-form { display: grid; gap: 9px; }
.login-form label { margin-top: 9px; color: var(--muted); font-size: 12px; }

.login-form input {
  width: 100%;
  padding: 13px 14px;
  border: 1px solid #b8c9c4;
  border-radius: 7px;
  outline: none;
  color: var(--ink);
  background: #fff;
  font: inherit;
}

.login-form input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.login-message { min-height: 1.5em; margin: 8px 0 0; color: var(--muted); font-size: 12px; }
.login-message.error { color: #9b4025; }
.login-button { width: 100%; margin-top: 2px; padding-block: 13px; }
.privacy-note { margin: 28px 0 0; color: var(--muted); font-size: 10px; line-height: 1.65; }

@media (max-width: 700px) {
  .chat-shell { display: block; }
  .conversation-panel { min-height: auto; padding: 18px 16px; border-right: 0; border-bottom: 1px solid var(--line); }
  .conversation-list { display: flex; max-height: 92px; margin-top: 17px; overflow-x: auto; }
  .conversation-row { flex: 0 0 225px; }
  .conversation-item { min-width: 170px; }
  .panel-note { display: none; }
  .chat-panel, .message-list { min-height: 0; }
  .chat-heading { padding: 22px 18px; }
  .message-list { min-height: 45vh; padding: 28px 18px; }
  .composer { padding: 0 18px 18px; }
  .message { max-width: 94%; }
  .login-shell { display: block; }
  .login-intro { min-height: 42vh; padding: 48px 24px 36px; border-right: 0; }
  .login-intro h1 { font-size: clamp(44px, 15vw, 66px); }
  .login-lead { margin-top: 22px; }
  .algebra-mark { display: none; }
  .login-panel { padding: 0 16px 32px; }
  .login-card { padding: 30px 24px; border-radius: 3px 22px 3px 3px; }
}