html {
  background: var(--app-bg);
  color: var(--text-1);
  font-family: var(--font-body);
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--app-bg);
  color: var(--text-1);
}

body.problem-page-body {
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input,
textarea,
select {
  font: inherit;
}

button {
  border: 0;
  background: none;
  color: inherit;
  cursor: pointer;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  border-bottom: 1px solid var(--border-1);
  background: var(--surface-1);
}

.topbar-inner,
.page-shell {
  width: min(1320px, calc(100% - 48px));
  margin: 0 auto;
}

.topbar-inner {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 28px;
  min-height: 58px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.brand-mark {
  position: relative;
  width: 18px;
  height: 18px;
}

.brand-mark__signal::before,
.brand-mark__signal::after {
  content: "";
  position: absolute;
  border-radius: 999px;
}

.brand-mark__signal::before {
  left: 0;
  bottom: 1px;
  width: 14px;
  height: 4px;
  background: var(--accent);
  transform: rotate(-42deg);
}

.brand-mark__signal::after {
  right: 0;
  top: 0;
  width: 8px;
  height: 8px;
  border: 2px solid var(--accent);
  background: transparent;
}

.brand-name {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 600;
}

.primary-nav {
  display: inline-flex;
  align-items: center;
  gap: 28px;
  min-width: 0;
}

.nav-link {
  color: var(--text-3);
  font-size: 1rem;
  line-height: 1;
  transition: color var(--transition-fast);
}

.nav-link:hover,
.nav-link:focus-visible,
.nav-link--active {
  color: var(--text-1);
  outline: none;
}

.topbar-actions {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  position: relative;
}

.theme-toggle,
.test-toggle,
.icon-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 34px;
}

.theme-toggle,
.test-toggle {
  padding: 0 10px;
  color: var(--text-3);
  transition: color var(--transition-fast);
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
  color: var(--text-1);
  outline: none;
}

.test-toggle:hover,
.test-toggle:focus-visible {
  color: var(--text-1);
  outline: none;
}

.test-utility {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.test-toggle {
  gap: 10px;
  min-height: 38px;
  padding: 0 12px 0 14px;
  border: 1px solid var(--border-1);
  border-radius: 999px;
  background: var(--surface-1);
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.06);
  transition:
    transform var(--transition-fast),
    box-shadow var(--transition-fast),
    color var(--transition-fast),
    border-color var(--transition-fast);
}

.test-toggle:hover,
.test-toggle:focus-visible {
  transform: translateY(-1px);
  box-shadow: 0 10px 22px rgba(0, 0, 0, 0.08);
}

.test-toggle__label,
.theme-toggle__label {
  font-size: 0.94rem;
}

.test-toggle__indicator {
  display: grid;
  place-items: center;
  width: 16px;
  height: 16px;
  border: 1px solid var(--border-2);
  border-radius: 999px;
  background: transparent;
  color: transparent;
  transition:
    background var(--transition-fast),
    border-color var(--transition-fast),
    color var(--transition-fast),
    transform var(--transition-fast);
}

.test-toggle__check {
  font-size: 0.7rem;
  line-height: 1;
}

.test-toggle[data-state="on"] .test-toggle__indicator {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--accent-contrast);
}

.test-bubble {
  position: relative;
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 0 6px;
  border: 1px solid rgba(209, 31, 31, 0.18);
  border-radius: 999px;
  background:
    linear-gradient(120deg, rgba(255, 255, 255, 0.22), rgba(255, 255, 255, 0) 35%),
    var(--accent-soft);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.06);
  transform: translateX(10px);
  opacity: 0;
  overflow: hidden;
}

.test-bubble[data-state="visible"] {
  animation: test-bubble-in 180ms ease forwards;
}

.test-bubble[data-state="leaving"] {
  animation: test-bubble-out 180ms ease forwards;
}

.test-bubble::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(100deg, transparent 20%, rgba(255, 255, 255, 0.5) 50%, transparent 80%);
  transform: translateX(-140%);
  pointer-events: none;
}

.test-bubble[data-state="visible"]::after {
  animation: test-bubble-sheen 520ms ease 120ms 1;
}

.test-bubble__button,
.test-bubble__input {
  position: relative;
  z-index: 1;
}

.test-bubble__button {
  width: 28px;
  height: 28px;
  border-radius: 999px;
  color: var(--text-1);
}

.test-bubble__button:disabled {
  opacity: 0.35;
  cursor: default;
}

.test-bubble__input {
  width: 44px;
  border: 0;
  background: transparent;
  color: var(--text-1);
  text-align: center;
}

.test-bubble__input:focus-visible {
  outline: none;
}

.test-bubble__input::-webkit-outer-spin-button,
.test-bubble__input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.test-bubble__input[type="number"] {
  -moz-appearance: textfield;
}

@keyframes test-bubble-in {
  from {
    opacity: 0;
    transform: translateX(10px);
  }

  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes test-bubble-out {
  from {
    opacity: 1;
    transform: translateX(0);
  }

  to {
    opacity: 0;
    transform: translateX(8px);
  }
}

@keyframes test-bubble-sheen {
  from {
    transform: translateX(-140%);
  }

  to {
    transform: translateX(140%);
  }
}

.test-bubble[hidden] {
  display: none !important;
}

.icon-button {
  width: 34px;
  padding: 0;
}

.icon-button__avatar {
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 999px;
  background: var(--color-gray-400);
  color: var(--color-black-950);
  font-size: 0.8rem;
  font-weight: 700;
}

.page-shell {
  padding: 72px 0 96px;
}

.hero {
  width: 100%;
}

.eyebrow {
  margin: 0 0 18px;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  text-transform: uppercase;
}

.hero h1 {
  margin: 0;
  padding-bottom: 20px;
  font-family: var(--font-display);
  font-size: clamp(3.2rem, 8vw, 5.8rem);
  line-height: 0.96;
  max-width: none;
}

.hero-text {
  margin: 0;
  color: var(--text-2);
  font-size: 1.08rem;
  line-height: 1.75;
  max-width: none;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: 32px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 42px;
  padding: 0 16px;
  border: 1px solid var(--border-1);
  border-radius: 8px;
  transition:
    background var(--transition-fast),
    border-color var(--transition-fast),
    color var(--transition-fast);
}

.button:focus-visible,
.nav-link:focus-visible,
.theme-toggle:focus-visible,
.dev-toggle:focus-visible {
  outline: 3px solid var(--focus-ring);
  outline-offset: 3px;
}

.button--primary {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--accent-contrast);
}

.button--primary:hover,
.button--primary:focus-visible {
  background: var(--accent-hover);
}

.button--secondary {
  background: transparent;
  color: var(--text-1);
}

.button--secondary:hover,
.button--secondary:focus-visible {
  border-color: var(--border-2);
  color: var(--text-1);
}

.problems-page {
  display: grid;
  gap: 40px;
}

.page-intro {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 480px);
  gap: 32px;
  align-items: end;
}

.page-title {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(2.6rem, 6vw, 4.6rem);
  line-height: 0.98;
}

.page-intro__text {
  margin: 0;
  color: var(--text-2);
  font-size: 1.02rem;
  line-height: 1.75;
}

.summary-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0;
  border-top: 1px solid var(--border-1);
  border-bottom: 1px solid var(--border-1);
}

.summary-item {
  padding: 18px 0;
}

.summary-item + .summary-item {
  padding-left: 24px;
  border-left: 1px solid var(--border-1);
}

.summary-item__label {
  display: block;
  margin-bottom: 6px;
  color: var(--text-3);
  font-family: var(--font-mono);
  font-size: 0.76rem;
  text-transform: uppercase;
}

.summary-item strong {
  font-family: var(--font-display);
  font-size: 1.22rem;
  font-weight: 600;
}

.problem-controls {
  display: grid;
  gap: 22px;
  padding: 20px 0 24px;
  border-top: 1px solid var(--border-1);
  border-bottom: 1px solid var(--border-1);
}

.problem-controls__top {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 16px;
  align-items: end;
}

.problem-controls__reset {
  min-height: 46px;
  padding-inline: 18px;
}

.search-field {
  display: grid;
  gap: 8px;
}

.search-field__label,
.filter-block__label {
  color: var(--text-3);
  font-family: var(--font-mono);
  font-size: 0.76rem;
  text-transform: uppercase;
}

.search-field input {
  width: 100%;
  min-height: 46px;
  padding: 0 14px;
  border: 1px solid var(--border-1);
  border-radius: 8px;
  background: var(--surface-1);
  color: var(--text-1);
}

.search-field input::placeholder {
  color: var(--text-3);
}

.search-field input:focus-visible {
  outline: 3px solid var(--focus-ring);
  outline-offset: -1px;
}

.filter-block {
  display: grid;
  gap: 10px;
}

.filter-grid {
  display: grid;
  grid-template-columns: 1.25fr 1fr 1fr;
  gap: 18px 28px;
  align-items: start;
}

.filter-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.filter-chip {
  min-height: 34px;
  padding: 0 12px;
  border: 1px solid var(--border-1);
  border-radius: 999px;
  background: transparent;
  color: var(--text-2);
  transition:
    border-color var(--transition-fast),
    color var(--transition-fast),
    background var(--transition-fast);
}

.filter-chip:hover,
.filter-chip:focus-visible,
.filter-chip--active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--text-1);
  outline: none;
}

.problem-list-section {
  display: grid;
  gap: 0;
}

.problem-list-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 14px 0;
  border-bottom: 1px solid var(--border-1);
}

.problem-list-header__titles {
  display: grid;
  grid-template-columns: minmax(420px, 1fr) 170px 120px 120px;
  gap: 18px;
  flex: 1;
  color: var(--text-3);
  font-family: var(--font-mono);
  font-size: 0.76rem;
  text-transform: uppercase;
}

.problem-count {
  margin: 0;
  color: var(--text-3);
  font-size: 0.94rem;
}

.problem-list {
  display: grid;
  border-top: 1px solid var(--border-1);
}

.problem-row {
  display: grid;
  grid-template-columns: minmax(420px, 1fr) 170px 120px 120px;
  gap: 18px;
  align-items: center;
  padding: 18px 12px;
  border-bottom: 1px solid var(--border-1);
  margin: 0 -12px;
  border-radius: 8px;
  transition: background var(--transition-fast), color var(--transition-fast);
}

.problem-row:hover,
.problem-row:focus-visible {
  background: var(--surface-3);
  outline: none;
}

.problem-row__main {
  display: grid;
  grid-template-columns: 72px minmax(0, 1fr);
  gap: 16px;
  align-items: start;
  min-width: 0;
}

.problem-row__number {
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.94rem;
}

.problem-row__copy {
  min-width: 0;
}

.problem-row__title {
  display: block;
  font-size: 1.3rem;
  line-height: 1.35;
}

.problem-row__copy p {
  margin: 6px 0 0;
  max-width: 780px;
  color: var(--text-2);
  font-size: 0.94rem;
  line-height: 1.55;
}

.problem-row__meta {
  display: grid;
  gap: 4px;
  color: var(--text-2);
  font-size: 0.96rem;
}

.problem-row__mobile-label {
  color: var(--text-3);
  font-family: var(--font-mono);
  font-size: 0.76rem;
  text-transform: uppercase;
}

.problem-row__mobile-label {
  display: none;
}

.status-tag {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  background: var(--surface-3);
  color: var(--text-1);
  font-size: 0.84rem;
}

.problem-empty {
  padding: 28px 0;
  color: var(--text-2);
}

.problem-page {
  display: grid;
  gap: 0;
  width: min(1368px, calc(100% - 24px));
  margin-left: 24px;
  margin-right: 0;
  padding-top: 32px;
}

body.problem-page-body .problem-page {
  flex: 1 1 auto;
  width: 100%;
  margin-left: 0;
  margin-right: 0;
  min-height: 0;
  padding-top: 24px;
  padding-left: 24px;
  padding-bottom: 24px;
  overflow: hidden;
}

.problem-layout {
  width: 100%;
  margin-left: 0;
  min-height: 0;
}

.problem-two-column {
  display: grid;
  grid-template-columns: 272px minmax(0, 1fr);
  gap: 40px;
  align-items: start;
  min-height: 0;
}

body.problem-page-body .problem-layout,
body.problem-page-body .problem-two-column {
  height: 100%;
}

.question-nav {
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  gap: 14px;
  padding-right: 24px;
  border-right: 1px solid var(--border-1);
  min-height: 0;
}

.question-nav__header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
}

.question-nav__header strong {
  font-size: 0.95rem;
  font-weight: 600;
}

.question-nav__list {
  display: grid;
  min-height: 0;
  overflow-y: auto;
  padding-right: 10px;
}

.question-nav__empty {
  color: var(--text-3);
  font-size: 0.94rem;
  line-height: 1.6;
}

.question-nav__item {
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr);
  gap: 12px;
  align-items: start;
  padding: 12px 0;
  border-bottom: 1px solid var(--border-1);
  color: var(--text-2);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.question-nav__item:hover,
.question-nav__item:focus-visible {
  color: var(--text-1);
  outline: none;
}

.question-nav__item--active {
  color: var(--text-1);
}

.question-nav__number {
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.88rem;
}

.question-nav__title {
  line-height: 1.5;
}

.problem-main {
  display: grid;
  gap: 28px;
  min-height: 0;
  align-content: start;
  padding-right: 24px;
}

body.problem-page-body .question-nav,
body.problem-page-body .problem-main {
  align-self: stretch;
}

body.problem-page-body .question-nav__list,
body.problem-page-body .problem-main {
  overflow-y: auto;
  scrollbar-gutter: stable;
}

.problem-header {
  display: grid;
  gap: 16px;
  padding-bottom: 22px;
  border-bottom: 1px solid var(--border-1);
}

.page-title--problem {
  font-size: clamp(2rem, 4vw, 3rem);
  line-height: 1.02;
}

.problem-header__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  color: var(--text-2);
}

.problem-header__meta-wrap {
  display: grid;
  gap: 14px;
}

.problem-header__meta span,
.problem-tag {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid var(--border-1);
  background: var(--surface-3);
  font-size: 0.9rem;
}

.problem-tag {
  position: relative;
  transition:
    border-color var(--transition-fast),
    background var(--transition-fast),
    color var(--transition-fast);
}

.problem-tag-toggle {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 12px;
  border: 1px solid var(--border-1);
  border-radius: 999px;
  background: var(--surface-1);
  color: var(--text-2);
  transition:
    border-color var(--transition-fast),
    background var(--transition-fast),
    color var(--transition-fast);
}

.problem-tag-toggle:hover,
.problem-tag-toggle:focus-visible {
  border-color: var(--border-2);
  color: var(--text-1);
  outline: none;
}

.problem-tag-toggle--revealed {
  color: var(--text-1);
  background: var(--surface-3);
}

.problem-tag--concealed {
  border-style: dashed;
  color: var(--text-3);
  background:
    linear-gradient(90deg, color-mix(in srgb, var(--surface-3) 90%, transparent), var(--surface-1));
}

.button--ghost {
  border-color: transparent;
  background: transparent;
  color: var(--text-2);
}

.button--ghost:hover,
.button--ghost:focus-visible {
  border-color: var(--border-1);
  background: var(--surface-3);
  color: var(--text-1);
}

.modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 80;
  display: grid;
  place-items: center;
  padding: 24px;
  background: rgba(15, 18, 24, 0.4);
  backdrop-filter: blur(4px);
}

.modal {
  width: min(100%, 32rem);
  display: grid;
  gap: 18px;
  padding: 22px;
  border: 1px solid var(--border-1);
  border-radius: 20px;
  background: var(--surface-1);
  box-shadow: 0 24px 70px rgba(0, 0, 0, 0.18);
}

.modal--compact {
  width: min(100%, 30rem);
}

.modal__header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
}

.modal__title {
  margin: 0;
  font-family: var(--font-display);
  font-size: 1.5rem;
}

.modal__close {
  width: 34px;
  height: 34px;
  padding: 0;
  border-radius: 999px;
  color: var(--text-2);
}

.modal__close:hover {
  background: var(--surface-3);
  color: var(--text-1);
}

.modal__close:focus-visible {
  outline: 3px solid var(--focus-ring);
  outline-offset: 2px;
}

.modal__body {
  margin: 0;
  color: var(--text-2);
  line-height: 1.65;
}

.modal__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.prose {
  color: var(--text-1);
  line-height: 1.75;
}

.prose p {
  margin: 0 0 16px;
}

.prose p:last-child {
  margin-bottom: 0;
}

.equation {
  font-family: var(--font-mono);
  line-height: 1.9;
  white-space: normal;
  text-align: center;
}

.answer-panel {
  display: grid;
  gap: 16px;
  justify-items: center;
  padding: 20px 0 24px;
  border-top: 1px solid var(--border-1);
  border-bottom: 1px solid var(--border-1);
  text-align: center;
}

.answer-panel .search-field {
  width: min(100%, 28rem);
  justify-items: center;
}

.answer-panel .search-field__label {
  width: 100%;
  text-align: center;
}

.answer-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
}

.answer-feedback {
  margin: 0;
  color: var(--text-2);
  min-height: 24px;
  text-align: center;
}

.answer-feedback[data-state="correct"] {
  color: var(--color-success);
}

.answer-feedback[data-state="incorrect"] {
  color: var(--accent);
}

.problem-section {
  display: grid;
  gap: 16px;
}

.problem-section__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.problem-section__header h2 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 1.4rem;
}

.problem-section__note {
  color: var(--text-3);
  font-size: 0.9rem;
}

.problem-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.profile-page,
.dashboard-page {
  display: grid;
  gap: 28px;
}

.profile-header,
.profile-section,
.profile-empty-state {
  display: grid;
  gap: 18px;
}

.profile-header {
  padding-bottom: 26px;
  border-bottom: 1px solid var(--border-1);
}

.profile-header__identity {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 20px;
  align-items: start;
}

.profile-avatar {
  display: grid;
  place-items: center;
  width: 76px;
  height: 76px;
  border-radius: 24px;
  background:
    linear-gradient(145deg, color-mix(in srgb, var(--accent) 22%, transparent), transparent),
    var(--surface-3);
  border: 1px solid var(--border-1);
  color: var(--text-1);
  font-family: var(--font-display);
  font-size: 2rem;
  font-weight: 600;
}

.profile-header__copy {
  display: grid;
  gap: 12px;
}

.profile-header__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  color: var(--text-2);
}

.profile-badge-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.profile-stat-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}

.profile-stat-card {
  display: grid;
  gap: 10px;
  min-height: 132px;
  padding: 18px;
  border: 1px solid var(--border-1);
  border-radius: 18px;
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--surface-3) 70%, transparent), transparent),
    var(--surface-1);
}

.profile-stat-card strong {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 600;
  line-height: 1;
}

.profile-stat-subgrid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 18px;
}

.profile-stat-subgrid__item {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  min-height: 38px;
  padding: 0 14px;
  border: 1px solid var(--border-1);
  border-radius: 999px;
  background: var(--surface-1);
  color: var(--text-2);
}

.profile-breakdown-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.profile-breakdown-card {
  display: grid;
  gap: 18px;
  padding: 18px;
  border: 1px solid var(--border-1);
  border-radius: 18px;
  background: var(--surface-1);
}

.profile-breakdown {
  display: grid;
  gap: 14px;
}

.profile-breakdown__row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 18px;
  align-items: center;
}

.profile-breakdown__copy {
  display: grid;
  gap: 4px;
}

.profile-breakdown__copy strong {
  font-size: 1rem;
  font-weight: 600;
}

.profile-breakdown__copy span {
  color: var(--text-2);
  font-size: 0.94rem;
}

.profile-breakdown__value {
  display: grid;
  gap: 8px;
  justify-items: end;
  min-width: 120px;
}

.profile-breakdown__value span {
  color: var(--text-2);
  font-family: var(--font-mono);
  font-size: 0.84rem;
}

.profile-breakdown__bar {
  width: 120px;
  height: 8px;
  border-radius: 999px;
  background: var(--surface-3);
  overflow: hidden;
}

.profile-breakdown__bar span {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 72%, white));
}

.profile-banner {
  padding: 14px 16px;
  border: 1px solid var(--border-1);
  border-radius: 14px;
  background:
    linear-gradient(120deg, color-mix(in srgb, var(--accent) 10%, transparent), transparent),
    var(--surface-1);
}

.profile-banner p,
.profile-section__hint {
  margin: 0;
  color: var(--text-2);
  line-height: 1.65;
}

.profile-activity-list {
  display: grid;
  gap: 12px;
}

.profile-activity-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 16px 18px;
  border: 1px solid var(--border-1);
  border-radius: 14px;
  background: var(--surface-1);
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.profile-activity-item:hover,
.profile-activity-item:focus-visible {
  border-color: var(--border-2);
  background: var(--surface-3);
  outline: none;
}

.profile-activity-item__main,
.profile-activity-item__copy {
  display: grid;
  gap: 6px;
}

.profile-activity-item__copy strong {
  font-size: 1rem;
  font-weight: 600;
}

.profile-activity-item__copy span {
  color: var(--text-2);
  font-size: 0.94rem;
}

.problem-list-header--profile {
  padding-top: 0;
}

.problem-list-header__titles--profile,
.problem-row--profile {
  grid-template-columns: minmax(340px, 1fr) 160px 120px 140px 140px;
}

.outcome-tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid transparent;
  background: var(--surface-3);
  color: var(--text-1);
  font-size: 0.84rem;
  white-space: nowrap;
}

.outcome-tag--flawless {
  background: color-mix(in srgb, var(--color-success) 18%, transparent);
  color: var(--color-success);
}

.outcome-tag--assisted {
  background: color-mix(in srgb, var(--accent) 14%, transparent);
  color: var(--text-1);
}

.outcome-tag--reviewed {
  background: color-mix(in srgb, var(--color-warning) 18%, transparent);
  color: var(--text-1);
}

.outcome-tag--in_progress {
  background: var(--surface-3);
  color: var(--text-2);
}

.outcome-tag--unsolved {
  background: transparent;
  border-color: var(--border-1);
  color: var(--text-2);
}

.dashboard-intro {
  align-items: start;
}

.dashboard-intro__actions {
  display: grid;
  gap: 14px;
}

.hint-list {
  display: grid;
  gap: 12px;
}

.hint-item {
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr);
  gap: 16px;
  padding: 18px;
  border: 1px solid var(--border-1);
  border-radius: 18px;
  background: var(--surface-1);
  transition:
    border-color var(--transition-fast),
    background var(--transition-fast);
}

.hint-item--locked {
  background:
    linear-gradient(135deg, color-mix(in srgb, var(--surface-3) 72%, transparent), transparent),
    var(--surface-1);
}

.hint-item--revealed {
  border-color: color-mix(in srgb, var(--accent) 30%, var(--border-1));
  background:
    linear-gradient(135deg, color-mix(in srgb, var(--accent) 10%, transparent), transparent),
    var(--surface-1);
}

.hint-item__index {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: 14px;
  background: var(--surface-3);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.95rem;
}

.hint-item__content {
  display: grid;
  gap: 8px;
}

.hint-item__eyebrow {
  color: var(--text-3);
  font-family: var(--font-mono);
  font-size: 0.76rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.hint-item h3 {
  margin: 0;
  font-size: 1.05rem;
}

.hint-item p {
  margin: 0;
  color: var(--text-2);
  line-height: 1.7;
}

.hint-item__answer[hidden] {
  display: none !important;
}

@media (max-width: 900px) {
  body.problem-page-body {
    display: block;
    height: auto;
    overflow: auto;
  }

  .topbar-inner {
    grid-template-columns: 1fr;
    gap: 14px;
    padding: 14px 0;
  }

  .primary-nav {
    gap: 20px;
  }

  .topbar-actions {
    justify-content: flex-start;
  }

  .page-shell {
    padding-top: 56px;
  }

  .page-intro {
    grid-template-columns: 1fr;
  }

  .summary-strip {
    grid-template-columns: 1fr;
  }

  .summary-item + .summary-item {
    padding-left: 0;
    border-left: 0;
    border-top: 1px solid var(--border-1);
  }

  .filter-grid {
    grid-template-columns: 1fr;
  }

  .profile-stat-grid,
  .profile-breakdown-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .problem-list-header {
    display: none;
  }

  .problem-row {
    grid-template-columns: 1fr;
    gap: 10px;
    padding: 18px 0 20px;
    margin: 0;
    border-radius: 0;
  }

  .problem-row__main {
    grid-template-columns: 64px minmax(0, 1fr);
  }

  .problem-row__meta {
    grid-template-columns: 96px minmax(0, 1fr);
    align-items: baseline;
  }

  .problem-row__mobile-label {
    display: inline;
    grid-row: 1 / span 2;
  }

  .problem-two-column {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .question-nav {
    padding-right: 0;
    padding-bottom: 18px;
    border-right: 0;
    border-bottom: 1px solid var(--border-1);
  }

  body.problem-page-body .problem-page,
  body.problem-page-body .problem-layout,
  body.problem-page-body .problem-two-column,
  body.problem-page-body .question-nav,
  body.problem-page-body .problem-main,
  body.problem-page-body .question-nav__list {
    height: auto;
    min-height: 0;
    overflow: visible;
  }

  .problem-section__header {
    align-items: flex-start;
    flex-direction: column;
  }

  .hint-item {
    grid-template-columns: 1fr;
  }

  .profile-header__identity,
  .profile-breakdown__row,
  .profile-activity-item {
    grid-template-columns: 1fr;
  }

  .profile-activity-item {
    flex-direction: column;
    align-items: start;
  }
}

@media (max-width: 640px) {
  .topbar-inner,
  .page-shell {
    width: min(100% - 24px, 1320px);
  }

  .problem-page {
    width: calc(100% - 12px);
    margin-left: 12px;
  }

  body.problem-page-body .problem-page {
    width: calc(100% - 12px);
    margin-left: 12px;
    margin-right: 0;
    padding-top: 16px;
    padding-left: 0;
    padding-bottom: 16px;
  }

  .primary-nav {
    gap: 16px;
    overflow-x: auto;
  }

  .hero h1 {
    font-size: clamp(2.6rem, 14vw, 4rem);
  }

  .hero-text {
    font-size: 1rem;
  }

  .page-title {
    font-size: clamp(2.2rem, 11vw, 3.2rem);
  }

  .problem-row__main {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  .problem-controls__top {
    grid-template-columns: 1fr;
  }

  .problem-controls__reset {
    justify-self: start;
  }

  .profile-stat-grid,
  .profile-breakdown-grid {
    grid-template-columns: 1fr;
  }

  .profile-header__identity {
    grid-template-columns: 1fr;
  }

  .profile-avatar {
    width: 64px;
    height: 64px;
    border-radius: 20px;
    font-size: 1.7rem;
  }
}