/* Page frame: top bar, outline, main area. */
.topbar { position: sticky; top: 0; z-index: 30; display: flex; align-items: center; gap: 14px; height: var(--header); padding: 0 16px; background: var(--panel); border-bottom: 1px solid var(--border); }
.brand { flex-shrink: 0; display: flex; align-items: center; gap: 10px; color: var(--text); font-weight: 700; font-size: 18px; text-decoration: none; }
.brand-mark { display: block; flex: none; width: 36px; height: 36px; border-radius: 0; padding: 0; object-fit: contain; background: transparent; box-shadow: none; }
.topbar-progress { display: flex; align-items: center; gap: 10px; width: 220px; font-size: 14px; color: var(--muted); white-space: nowrap; }
.shell { display: grid; grid-template-columns: 290px minmax(0, 1fr); height: calc(100dvh - var(--header)); }
body.outline-hidden .shell { grid-template-columns: 0 minmax(0, 1fr); }
body.outline-hidden .outline { visibility: hidden; padding: 0; border: 0; }
main { min-width: 0; overflow: auto; }
main:focus { outline: none; }
.view { min-height: 100%; }
#view-exercise { display: flex; flex-direction: column; height: 100%; min-height: 0; }
.missing { display: grid; place-content: center; justify-items: start; gap: 12px; padding: 40px; }

.outline { overflow: auto; padding: 18px 14px 28px; background: #090d15; border-right: 1px solid var(--border); }
.outline-home { display: inline-block; margin: 0 6px 14px; font-size: 15px; text-decoration: none; }
.outline-chapter > summary { padding: 8px 8px; font-weight: 700; font-size: 16px; cursor: pointer; }
.outline-lesson { margin-left: 8px; }
.outline-lesson > summary { padding: 6px 8px; font-size: 15px; color: var(--muted); cursor: pointer; }
.outline-links { display: grid; gap: 2px; margin: 2px 0 8px 6px; }
.outline-link { border: 0; background: transparent; font-family: inherit; text-align: left; cursor: pointer; display: flex; align-items: center; gap: 10px; padding: 7px 10px; border-radius: var(--radius); color: #d3def7; font-size: 15px; text-decoration: none; }
.outline-link:hover { background: #19222f; }
.outline-link:is([aria-current=page], [aria-current=step]) { background: #123650; color: #b6f7ff; }
.outline-mark { display: grid; place-items: center; flex: none; width: 22px; height: 22px; border: 1px solid #65738f; border-radius: 50%; font-size: 13px; }
.outline-link.done .outline-mark { border-color: var(--green); color: var(--green); }
.outline-backdrop { display: none; }

@media (max-width: 1099px) {
  .shell { display: block; height: auto; }
  main { height: calc(100dvh - var(--header)); }
  .outline { position: fixed; z-index: 40; top: var(--header); bottom: 0; left: 0; width: min(320px, 88vw); transform: translateX(-100%); visibility: hidden; transition: transform 0.2s ease; }
  body.outline-open .outline { transform: none; visibility: visible; }
  body.outline-open .outline-backdrop { display: block; position: fixed; z-index: 35; inset: var(--header) 0 0 0; background: rgba(6, 8, 15, 0.6); }
  .topbar-progress { width: 130px; }
}
@media (max-width: 520px) { .topbar-progress span { display: none; } .topbar-progress { width: 90px; } }
.outline-missing { margin: 4px 8px; font-size: 14px; color: #acbddf; }
.lesson-row.unavailable { opacity: 0.6; }

@media (max-width: 380px) { .topbar { gap: 8px; padding: 0 10px; } .brand { gap: 7px; font-size: 16px; } .topbar-progress { width: 56px; min-width: 0; } }

#account-button { margin-left: 0; min-height: 36px; padding: 4px 12px; font-size: 14px; }
.account-dialog { width: min(480px, calc(100% - 32px)); max-width: none; max-height: calc(100dvh - 32px); padding: 0; overflow: auto; border: 1px solid var(--border-strong); border-radius: 12px; background: var(--panel); color: var(--text); box-shadow: 0 24px 80px #0008; }
.account-dialog::backdrop { background: rgba(6, 8, 15, 0.75); }
.account-dialog-header { position: sticky; top: 0; z-index: 1; display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 20px 24px; border-bottom: 1px solid var(--border); background: var(--panel); }
.account-dialog-header h2 { min-width: 0; margin: 0; font-size: 24px; }
.account-dialog-header .btn { flex: none; min-height: 40px; }
.account-dialog-body { display: grid; gap: 20px; padding: 24px; }
.account-dialog-body p { margin: 0; }
.account-dialog .account-introduction { color: var(--muted); font-size: 15px; }
.account-dialog .account-form { gap: 18px; }
.account-dialog .field { display: grid; grid-template-columns: minmax(0, 1fr); gap: 8px; margin: 0; }
.account-dialog .field input { width: 100%; min-height: 46px; }
.account-dialog .account-primary { width: 100%; min-height: 46px; }
.account-dialog .account-message:empty, .account-resume:empty { display: none; }
.account-secondary-actions { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
.account-secondary-actions .btn { padding: 10px; font-size: 14px; }
.account-email { font-size: 17px; overflow-wrap: anywhere; }
.account-dialog .dialog-actions { margin: 0; }
.account-dialog .dialog-actions .btn { width: 100%; }
.account-danger { padding: 16px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--sunken); }
.account-danger summary { cursor: pointer; font-size: 15px; }
.account-danger[open] { display: grid; gap: 14px; border-color: var(--error); }
.account-danger[open] summary { margin-bottom: 14px; }
.account-danger[open] p, .account-danger[open] .field { margin-bottom: 14px; }
.account-danger > .btn { width: 100%; border-color: var(--error); color: var(--error); }
.account-dialog-footer { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding: 16px 24px; border-top: 1px solid var(--border); }
.account-version { margin-left: auto; color: var(--muted); font-size: 13px; font-variant-numeric: tabular-nums; }
@media (max-width: 420px) {
  .account-dialog { width: calc(100% - 20px); max-height: calc(100dvh - 20px); }
  .account-dialog-header, .account-dialog-body, .account-dialog-footer { padding: 18px; }
  .account-dialog-header h2 { font-size: 22px; }
  .account-secondary-actions { grid-template-columns: minmax(0, 1fr); }
}
.account-form { display: grid; gap: 12px; }
.account-message { min-height: 1.4em; margin: 0; color: var(--muted); }
.dialog-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }

.study { max-width: 760px; margin: 0 auto; padding: 24px 16px 64px; }
.study-section { margin-top: 24px; }
.study-list { padding-left: 20px; display: grid; gap: 8px; }
.study-note { margin: 4px 0 0; color: var(--muted); white-space: pre-wrap; }
.study-empty { color: var(--muted); }
.class-card { margin: 12px 0; padding: 12px 16px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--panel); }
.class-card h3 { margin-top: 0; }
.class-table { width: 100%; border-collapse: collapse; margin-top: 12px; }
.class-table th, .class-table td { padding: 6px 8px; border-bottom: 1px solid var(--border); text-align: left; }
#search-box { padding: 8px 12px; }
#search-input { width: 100%; padding: 8px; border: 1px solid var(--border-strong); border-radius: var(--radius); background: var(--sunken); color: var(--text); font: inherit; }
.search-results { list-style: none; margin: 8px 0 0; padding: 0; display: grid; gap: 8px; }
.search-snippet { display: block; color: var(--muted); font-size: 13px; }
.search-option { padding: 6px 8px; border-radius: var(--radius); }
.search-option a, .search-title { font-weight: 600; }
.search-option[aria-selected="true"] { outline: 2px solid var(--border-strong); background: var(--raised); }
.search-where { display: block; color: var(--muted); font-size: 13px; }
.nav-badge { display: inline-block; min-width: 18px; margin-left: 6px; padding: 0 5px; border-radius: 9px; background: var(--border-strong); color: var(--text); font-size: 13px; line-height: 18px; text-align: center; }

.mobile-main-menu { display: none; }
@media (max-width: 700px) {
  .topbar { gap: 8px; padding: 0 10px; }
  .topbar .brand span, .topbar .topnav, .topbar .topbar-progress { display: none; }
  .mobile-main-menu { display: block; margin-left: auto; }
  .mobile-main-menu summary { cursor: pointer; padding: 10px 4px; }
  .mobile-main-menu nav { position: absolute; right: 10px; top: 100%; display: grid; padding: 12px; background: var(--panel); border: 1px solid var(--border); }
  .mobile-main-menu a { padding: 12px; }
  #account-button { padding: 4px 8px; }
}

.loading-status {
  position: fixed;
  bottom: 12px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 80;
  width: min(320px, calc(100% - 24px));
  padding: 10px 14px;
  background: var(--panel);
  color: var(--text);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  font-size: 14px;
  box-shadow: 0 8px 24px #0006;
  pointer-events: none;
}
.loading-status progress { display: block; width: 100%; margin-top: 6px; height: 6px; }
@media (prefers-reduced-motion: reduce) {
  .loading-status progress { animation: none; }
}

#view-exercise[aria-busy="true"] > * { opacity: 0; pointer-events: none; }
.loading-status progress:indeterminate {
  background: linear-gradient(90deg, var(--border) 20%, var(--green) 50%, var(--border) 80%);
  background-size: 200% 100%;
}
.loading-status progress:indeterminate::-webkit-progress-bar { background: transparent; }
.loading-status progress:indeterminate::-moz-progress-bar { background: transparent; }
@media (prefers-reduced-motion: no-preference) {
  .loading-status progress:indeterminate { animation: request-wait 1.4s linear infinite; }
}
@keyframes request-wait { from { background-position: 200% 0; } to { background-position: 0 0; } }
html[data-reduce-motion="1"] .loading-status progress { animation: none; }

.error-banner { width: max-content; overflow-wrap: anywhere; }

.outline-label { display: none; }
@media (max-width: 1099px) { #outline-toggle { width: auto; padding: 0 12px; } .outline-label { display: inline; margin-left: 6px; } }
.show-password { display: flex; align-items: center; gap: 6px; font-size: 14px; color: var(--muted); }
.search-none { padding: 6px 4px; color: var(--muted); font-size: 14px; list-style: none; }

.account-name-fields { display: grid; gap: 18px; }

.google-auth { width: 100%; background: #fff; color: #1f1f1f; border-color: #747775; gap: 12px; }
.google-auth img { object-fit: contain; flex: none; }

.learning-route .topnav a[href="/pricing"], .learning-route .mobile-main-menu a[href="/pricing"] { display: none; }

.account-dialog.is-signed-in { width: min(640px, calc(100% - 32px)); }
.account-dialog .account-name-fields { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.account-dialog .account-section { display: grid; gap: 14px; padding-top: 20px; border-top: 1px solid var(--border); min-width: 0; }
.account-section h3 { margin: 0; font-size: 17px; }
.account-section .btn { justify-self: start; }
.account-dialog .account-section .account-form { display: grid; gap: 14px; }
.account-dialog .account-identity { display: grid; gap: 10px; }
.account-email-badge { justify-self: start; padding: 4px 9px; border: 1px solid var(--border-strong); border-radius: 4px; color: var(--muted); font-size: 13px; }
.account-email-badge.is-confirmed { color: var(--green); border-color: var(--green); }
.account-dialog .account-message { color: var(--muted); font-size: 14px; overflow-wrap: anywhere; }
.account-dialog .account-close { width: 40px; padding: 4px; font-size: 27px; line-height: 1; }
.account-password { border: 1px solid var(--border); padding: 14px; background: var(--sunken); }
.account-password > summary { cursor: pointer; font-weight: 600; }
.account-password[open] > summary { margin-bottom: 16px; }
.account-password > .study-note { margin: 16px 0 10px; }
.account-verification { display: grid; gap: 12px; }
.account-dialog .field input { min-width: 0; box-sizing: border-box; }
@media (max-width: 440px) {
  .account-dialog .account-name-fields { grid-template-columns: minmax(0, 1fr); }
  .account-dialog.is-signed-in { width: calc(100% - 20px); }
}

.account-dialog::backdrop { backdrop-filter: blur(4px); }

.account-dialog.is-signed-in { width: min(960px, calc(100% - 32px)); }
.account-dialog.is-signed-in .account-dialog-header { padding: 16px 20px; }
.account-dialog.is-signed-in .account-dialog-body { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; padding: 18px 20px; align-items: start; }
.account-dialog.is-signed-in .account-identity { grid-column: 1 / -1; grid-template-columns: minmax(0, 1fr) auto; gap: 6px 12px; align-items: center; }
.account-dialog.is-signed-in .account-identity .account-message { grid-column: 1 / -1; }
.account-dialog.is-signed-in .account-section { gap: 10px; padding: 14px; border: 1px solid var(--border); border-radius: 6px; background: var(--sunken); }
.account-dialog.is-signed-in .account-section .account-form { gap: 10px; }
.account-dialog.is-signed-in .account-name-fields { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
@media (max-width: 440px) {
  /* The name fields and the new password fields use one column on a narrow screen. */
  .account-dialog.is-signed-in .account-name-fields, .account-dialog.is-signed-in .account-password .account-name-fields { grid-template-columns: 1fr; }
}
.account-dialog.is-signed-in .field { gap: 5px; font-size: 13px; }
.account-dialog.is-signed-in .field input { min-height: 40px; padding: 8px 10px; }
.account-dialog.is-signed-in .study-note { font-size: 13px; line-height: 1.5; }
.account-dialog.is-signed-in .account-verification { gap: 8px; font-size: 13px; }
.account-dialog.is-signed-in .account-password { padding: 10px; }
.account-dialog.is-signed-in .account-section-learning { display: flex; flex-wrap: wrap; align-items: start; }
.account-section-learning > h3 { flex-basis: 100%; }
.account-section-learning .account-resume:not(:empty) { display: contents; }
.account-dialog.is-signed-in .account-dialog-footer { position: sticky; bottom: 0; padding: 12px 20px; background: var(--panel); }
.account-dialog.is-signed-in .account-danger { padding: 10px; }
@media (max-width: 620px) {
  .account-dialog.is-signed-in .account-dialog-body { grid-template-columns: minmax(0, 1fr); padding: 14px; }
  .account-dialog.is-signed-in .account-identity { grid-template-columns: minmax(0, 1fr); }
  .account-dialog.is-signed-in .account-identity .account-message { grid-column: auto; }
}

.topbar { display: grid; grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr); }
.topbar-start, .topbar-end { display: flex; align-items: center; gap: 12px; min-width: 0; }
.topbar-start { justify-self: start; max-width: 100%; }
.topbar-end { justify-self: end; max-width: 100%; }
.topbar > .topnav { justify-self: center; margin: 0; }
.topbar-end .theme-toggle { margin-left: 0; }
.topbar-end .topbar-progress { min-width: 0; flex-shrink: 1; }
@media (max-width: 700px) {
  .topbar { display: flex; }
  .topbar-start { flex: 1; gap: 8px; }
  .topbar-end { flex: none; gap: 6px; }
}

.outline:has(#outline-tree:empty) { display: none; }
.shell:has(#outline-tree:empty) { grid-template-columns: minmax(0, 1fr); }
body:has(#outline-tree:empty) #outline-toggle { display: none; }

.account-icon-button { display: none; }
@media (max-width: 767px) {
  .mobile-main-menu summary { display: flex; align-items: center; min-height: 44px; padding: 10px 8px; }
  .topbar .brand { min-width: 44px; min-height: 44px; justify-content: center; }
  .topbar .theme-toggle, .topbar-end .theme-toggle { width: 44px; height: 44px; }   /* More specific than the 40px rule in theme.css. */
  .account-icon-button { display: inline-flex; align-items: center; justify-content: center; flex: none; width: 44px; height: 44px; padding: 8px; border: 1px solid transparent; border-radius: 8px; background: transparent; color: var(--text); cursor: pointer; }
  .account-icon-button:focus-visible { outline: 3px solid var(--amber); outline-offset: 2px; }
}

@media (max-width: 480px) {
  .site-footer a, .site-footer .link-button { display: inline-block; min-height: 44px; padding: 12px 8px; }
}

@media (min-width: 621px) and (max-width: 900px) {
  .account-dialog, .account-dialog.is-signed-in { width: calc(100vw - 32px); max-width: min(560px, calc(100vw - 32px)); }
  .account-dialog.is-signed-in .account-dialog-body { grid-template-columns: minmax(0, 1fr); }
  .account-dialog .account-section, .account-dialog .field { min-width: 0; }
}

@media (max-width: 480px) {
  .topbar #outline-toggle { min-width: 44px; min-height: 44px; }
}

/* Signed-in account dialog: four plain sections, every form visible. */
.account-dialog.is-signed-in .account-section { background: transparent; border: 0; border-top: 1px solid var(--border); border-radius: 0; padding: 16px 0 4px; }
.account-dialog.is-signed-in .account-section h3 { font-size: 15px; color: var(--muted); font-weight: 600; }
.account-subform { display: grid; gap: 10px; }