/* Lesson-page layouts, composed only from ui.css tokens and components. */

.lesson-prose p,
.lesson-prose li { font-size: var(--feed-text); line-height: 26px; }
.lesson-prose p + p { margin-top: var(--space-3); }
.lesson-prose strong { font-weight: 600; }
.lesson-prose ul { margin: var(--space-2) 0 0; padding-left: var(--space-5); }
.lesson-prose li + li { margin-top: var(--space-1); }
.lesson-lead { color: var(--text-secondary); margin-bottom: var(--space-4) !important; }

/* core idea */
.lesson-core { display: flex; flex-direction: column; gap: var(--space-3); }
.lesson-core .ops-inset p { margin-top: var(--space-1); font-size: var(--feed-text); line-height: 26px; }

/* glossary terms in running text */
.term {
  text-decoration: underline dotted var(--accent-500); text-decoration-thickness: 1px;
  text-underline-offset: 3px; cursor: help;
}

/* step-through (design system §9.14 "steps") */
.lesson-steps { list-style: none; margin: 0; padding: 0; }
.lesson-steps li {
  position: relative; padding: 0 0 var(--space-5) var(--space-6);
  font-size: var(--feed-text); line-height: 26px;
}
.lesson-steps li::before {
  content: ""; position: absolute; left: 4px; top: 7px; width: 12px; height: 12px;
  border-radius: var(--radius-full); background: var(--accent-500);
}
.lesson-steps li::after {
  content: ""; position: absolute; left: 9px; top: 24px; bottom: 4px; width: 2px; background: var(--border);
}
.lesson-steps li:last-child::after,
.lesson-steps li.is-current::after { display: none; }
.lesson-steps li.is-current::before { background: var(--surface); box-shadow: inset 0 0 0 2px var(--accent-500); }
.lesson-steps li[hidden] { display: none; }
.lesson-steps li.is-new { animation: lesson-in var(--duration) var(--ease-out); }
.lesson-steps .ops-label { display: block; color: var(--text-muted); }
@keyframes lesson-in { from { opacity: 0; transform: translateY(var(--space-1)); } to { opacity: 1; transform: none; } }
.lesson-steps-bar { display: flex; align-items: center; gap: var(--space-3); padding-top: var(--space-4); border-top: 1px solid var(--border); }
.lesson-steps-bar .ops-progress { flex: 1; max-width: 160px; }
.lesson-steps-bar .ops-meta { margin-left: auto; }

/* diagrams */
.lesson-diagram { overflow-x: auto; margin: 0; }
.lesson-diagram .mermaid { width: 100%; margin: 0; padding: 0; background: none; text-align: center; }
.lesson-diagram svg { display: block; margin: 0 auto; max-width: 100%; height: auto; }
.lesson-caption { margin-top: var(--space-3); color: var(--text-secondary); }

/* interactive widget */
.lesson-widget .ops-actions { margin-bottom: var(--space-4); }
.lesson-chart { width: 100%; display: block; }
.lesson-readout { display: flex; align-items: center; gap: var(--space-3); margin: var(--space-3) 0 var(--space-4); min-height: 22px; }
.lesson-slider { display: grid; grid-template-columns: 120px 1fr 56px; gap: var(--space-3); align-items: center; height: var(--row-h); }
.lesson-slider label { font: 500 13px/20px var(--font-sans); }
.lesson-slider output { font: 400 12px/16px var(--font-mono); text-align: right; color: var(--text-secondary); }
.lesson-slider input[type=range] { width: 100%; accent-color: var(--accent-500); }

/* think it through */
.lesson-think + .lesson-think { margin-top: var(--space-5); padding-top: var(--space-5); border-top: 1px solid var(--border); }
.lesson-think .ops-heading { margin-bottom: var(--space-3); }
.lesson-options { display: flex; flex-direction: column; gap: var(--space-2); }
.lesson-options .ops-btn { height: auto; min-height: 36px; padding: var(--space-2) var(--space-3); justify-content: space-between; text-align: left; }
.lesson-options .ops-btn[aria-pressed="true"] { border-color: var(--border-strong); background: var(--surface-subtle); }
.lesson-feedback { margin-top: var(--space-3); }
.lesson-feedback[hidden] { display: none; }
.lesson-feedback p { margin-top: var(--space-1); }

/* go deeper */
.lesson-deeper { list-style: none; margin: 0; padding: 0; }
.lesson-deeper li {
  display: flex; align-items: center; justify-content: space-between; gap: var(--space-4);
  padding: var(--space-3) 0; border-bottom: 1px solid var(--border);
}
.lesson-deeper li:first-child { padding-top: 0; }
.lesson-deeper li:last-child { border-bottom: 0; padding-bottom: 0; }
.lesson-deeper span { font-size: var(--feed-text); line-height: 24px; }

details.lesson-deep-dive { border: 1px solid var(--border); border-radius: var(--radius-md); background: var(--surface); }
details.lesson-deep-dive > summary { cursor: pointer; padding: var(--space-4) var(--section-pad); font: 600 16px/24px var(--font-sans); }
details.lesson-deep-dive > div { padding: 0 var(--section-pad) var(--section-pad); }

/* footer */
.lesson-foot { display: flex; align-items: center; justify-content: space-between; gap: var(--space-4); flex-wrap: wrap; }