/* ── Problem list ── */
.problem-list {
  list-style: none;
  display: flex;
  flex-direction: column;
}

/* ── Problem item ── */
.problem-item {
  padding: 2.5rem 0;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
}

.problem-item:last-child {
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

/* ── Header row: number + domain ── */
.problem-item__header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

.problem-item__num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  color: var(--text-dim);
  opacity: 0.4;
}

.problem-item__domain {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 0.2rem 0.55rem;
  opacity: 0.8;
}

/* ── Title ── */
.problem-item__title {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.2;
  margin-bottom: 1.75rem;
}

/* ── Content blocks ── */
.problem-item__block {
  margin-bottom: 1.25rem;
  padding-left: 1rem;
  border-left: 1px solid rgba(255, 255, 255, 0.1);
}

.problem-item__label {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-dim);
  opacity: 0.5;
  margin-bottom: 0.4rem;
}

.problem-item__text {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-dim);
  line-height: 1.75;
}

/* ── Tags (reuse from projects.css) ── */
.problem-item .project-item__tags {
  margin-top: 1.5rem;
}