:root {
  --mtu-gold: #ffcd00;
  --mtu-black: #000000;
  --mtu-dark: #454646;
  --mtu-white: #ffffff;
  --mtu-deep-gold: #fbad18;
  --mtu-copper: #dc662d;
  --mtu-teal: #3ec0c5;
  --mtu-sky: #8a8c8c;
  --surface: #f7f7f3;
  --line: #d9d9d2;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--mtu-black);
  background: var(--surface);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem clamp(1rem, 4vw, 3rem);
  background: var(--mtu-black);
  color: var(--mtu-white);
  border-bottom: 6px solid var(--mtu-gold);
}

.brand {
  display: flex;
  align-items: center;
  gap: .8rem;
  font-weight: 800;
  letter-spacing: 0;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 2.4rem;
  height: 2.4rem;
  background: var(--mtu-gold);
  color: var(--mtu-black);
  font-weight: 900;
}

.topbar small {
  color: #deded8;
}

main {
  width: min(1180px, calc(100% - 2rem));
  margin: 1.5rem auto 4rem;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(280px, .7fr);
  gap: 1.5rem;
  align-items: stretch;
  margin-bottom: 1.5rem;
}

.panel,
.step,
.feedback {
  background: var(--mtu-white);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.panel {
  padding: clamp(1rem, 3vw, 2rem);
}

h1,
h2,
h3 {
  margin: 0 0 .75rem;
  line-height: 1.1;
  letter-spacing: 0;
}

h1 {
  font-size: clamp(2rem, 5vw, 4rem);
}

h2 {
  font-size: 1.35rem;
}

p {
  line-height: 1.55;
}

.badge-row,
.actions,
.score-row {
  display: flex;
  flex-wrap: wrap;
  gap: .6rem;
  align-items: center;
}

.badge {
  display: inline-flex;
  align-items: center;
  min-height: 2rem;
  padding: .35rem .65rem;
  background: #fff6cf;
  border: 1px solid #ebc63b;
  font-size: .9rem;
  font-weight: 700;
}

.badge.dark {
  background: var(--mtu-dark);
  color: var(--mtu-white);
  border-color: var(--mtu-dark);
}

.grid {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 1.5rem;
}

.rail {
  display: grid;
  gap: .8rem;
  align-content: start;
}

.step {
  padding: 1rem;
}

.step strong {
  display: block;
  margin-bottom: .35rem;
}

.content {
  display: grid;
  gap: 1rem;
}

.lesson-block {
  padding: 1.2rem;
  background: var(--mtu-white);
  border-left: 6px solid var(--mtu-gold);
}

.equation {
  padding: .8rem;
  background: #f2f2ee;
  border: 1px solid var(--line);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  overflow-x: auto;
}

label {
  display: block;
  margin: .9rem 0 .35rem;
  font-weight: 750;
}

select,
input[type="text"],
input[type="file"] {
  width: 100%;
  min-height: 2.75rem;
  padding: .65rem .75rem;
  border: 1px solid #b9b9b0;
  border-radius: 6px;
  background: var(--mtu-white);
  font: inherit;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 2.75rem;
  padding: .7rem 1rem;
  border: 0;
  border-radius: 6px;
  background: var(--mtu-black);
  color: var(--mtu-white);
  font-weight: 800;
  text-decoration: none;
  cursor: pointer;
}

.button.secondary {
  background: var(--mtu-gold);
  color: var(--mtu-black);
}

.button.ghost {
  background: transparent;
  color: var(--mtu-black);
  border: 1px solid var(--mtu-black);
}

.feedback {
  padding: 1rem;
  border-left: 6px solid var(--mtu-teal);
}

.feedback.fail {
  border-left-color: var(--mtu-copper);
}

.feedback ul {
  padding-left: 1.1rem;
}

.score {
  font-size: 2.5rem;
  font-weight: 900;
}

.muted {
  color: var(--mtu-dark);
}

.table-preview {
  width: 100%;
  border-collapse: collapse;
  background: var(--mtu-white);
}

.table-preview th,
.table-preview td {
  border: 1px solid var(--line);
  padding: .55rem;
  text-align: left;
}

.table-preview th {
  background: var(--mtu-black);
  color: var(--mtu-white);
}

.details {
  margin-top: .8rem;
  padding: .8rem;
  background: #f5fbfb;
  border: 1px solid #b6e5e7;
}

@media (max-width: 820px) {
  .hero,
  .grid {
    grid-template-columns: 1fr;
  }

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