/* ---------- structured lesson: key points, formula boxes, inline checks ---------- */

/* the chapter objective this lesson delivers, above the intro.
   Gold-left-bordered like the handouts note, because it plays the same part: the author
   talking about the material rather than the material itself. */
.kp-objective {
    margin: 0 0 18px;
    padding: 13px 16px;
    background: var(--bg-raised);
    border: 1px solid var(--border);
    border-left: 3px solid var(--gold);
    border-radius: var(--radius);
}

.kp-obj-head {
    display: flex;
    align-items: baseline;
    gap: 12px;
    flex-wrap: wrap;
    font-family: 'IBM Plex Mono', monospace;
    font-size: .64rem;
    text-transform: uppercase;
    letter-spacing: .07em;
}

.kp-obj-label {
    font-weight: 700;
    color: var(--gold);
}

.kp-obj-shared {
    margin-left: auto;
    color: var(--text-muted);
}

.kp-obj-text {
    margin: 7px 0 0;
    font-size: .95rem;
    color: var(--text);
}

.kp-obj-src {
    margin: 8px 0 0;
    font-family: 'IBM Plex Mono', monospace;
    font-size: .63rem;
    text-transform: uppercase;
    letter-spacing: .05em;
    color: var(--text-muted);
}

.kp-obj-src b {
    color: var(--text-muted);
    font-weight: 700;
}

/* same treatment the glossary gives its "defined in" jump: a link that has to sit inside a
   mono meta line without becoming a button */
.kp-obj-src .link {
    font: inherit;
    text-transform: inherit;
    letter-spacing: inherit;
    color: var(--accent);
    font-weight: 700;
    text-decoration: underline;
    background: none;
    border: none;
    padding: 0;
    cursor: pointer;
}

/* progress strip at the top of a key-point lesson */
.kp-rail {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
    margin: 18px 0 26px;
    padding: 10px 14px;
    background: var(--bg-raised);
    border: 1px solid var(--border);
    border-radius: 2px;
    font-family: 'IBM Plex Mono', monospace;
    font-size: .7rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--text-muted);
}

.kp-rail-dots {
    display: flex;
    gap: 6px;
    margin-left: auto;
}

.kp-dot {
    width: 9px;
    height: 9px;
    border-radius: 50%;
    border: 1.5px solid var(--border-strong);
    background: transparent;
}

.kp-dot.done {
    background: var(--success);
    border-color: var(--success);
}

/* answered by reading the answer, not by working it out */
.kp-dot.shown {
    background: var(--border-strong);
    border-color: var(--border-strong);
}

/* one key point */
.keypoint {
    margin: 0 0 34px;
    padding-top: 22px;
    border-top: 1px dashed var(--border);
}

.keypoint:first-of-type {
    border-top: none;
    padding-top: 0;
}

.kp-head {
    display: flex;
    align-items: baseline;
    gap: 12px;
    margin-bottom: 10px;
}

.kp-num {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .72rem;
    letter-spacing: .08em;
    color: var(--accent);
    border: 1px solid var(--accent);
    border-radius: 2px;
    padding: 2px 6px;
    flex: none;
}

.kp-head h3 {
    margin: 0;
    font-size: 1.45rem;
    flex: 1;
}

.kp-flag {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .66rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--success);
    border: 1px solid var(--success);
    border-radius: 2px;
    padding: 2px 6px;
    display: none;
    flex: none;
}

.keypoint.checked .kp-flag {
    display: inline-block;
}

.keypoint.shown .kp-flag {
    display: inline-block;
    color: var(--text-muted);
    border-color: var(--border-strong);
}

.keypoint.flash {
    animation: kpFlash 1.4s ease-out;
}

@keyframes kpFlash {
    0% { background: var(--gold-soft); }
    100% { background: transparent; }
}

/* tags: a cross-cutting filter axis, not a hierarchy level */
.kp-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin: -4px 0 12px;
}

.kp-tag {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .62rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--text-muted);
    border: 1px dashed var(--border-strong);
    border-radius: 2px;
    padding: 2px 6px;
}

/* formula / rule card */
.formula-box {
    margin: 20px 0;
    padding: 0;
    border: 1px solid var(--border-strong);
    border-radius: 2px;
    background: var(--bg-raised);
    overflow: hidden;
}

.formula-box figcaption {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .66rem;
    text-transform: uppercase;
    letter-spacing: .08em;
    color: var(--text-muted);
    padding: 8px 16px;
    border-bottom: 1px dashed var(--border-strong);
    background: var(--bg-sunken);
}

.formula-exp {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .98rem;
    line-height: 1.7;
    text-align: center;
    color: var(--text);
    padding: 18px 16px;
}

.formula-exp .fx-accent {
    color: var(--accent);
    font-weight: 600;
}

.formula-exp .fx-sub {
    display: block;
    font-size: .78rem;
    color: var(--text-muted);
    margin-top: 6px;
}

.formula-legend {
    border-top: 1px dashed var(--border-strong);
    padding: 12px 16px;
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 4px 14px;
    font-size: .8rem;
    font-family: 'Public Sans', sans-serif;
    color: var(--text-muted);
}

.formula-legend dt {
    font-family: 'IBM Plex Mono', monospace;
    color: var(--text);
    font-size: .76rem;
}

.formula-legend dd {
    margin: 0;
}

.formula-worked {
    border-top: 1px dashed var(--border-strong);
    padding: 12px 16px;
    font-size: .84rem;
    font-family: 'Public Sans', sans-serif;
    color: var(--text-muted);
}

.formula-worked strong {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .74rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--text);
    display: block;
    margin-bottom: 4px;
}

/* diagram sits inside the formula card, under the expression */
.kp-diagram {
    border-top: 1px dashed var(--border-strong);
    padding: 14px 16px 10px;
    background: var(--bg);
}

.kp-diagram svg {
    display: block;
    width: 100%;
    height: auto;
    overflow: visible;
}

.kp-diagram .dg-label {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 9px;
    letter-spacing: .04em;
    fill: var(--text-muted);
}

.kp-diagram .dg-value {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 10px;
    fill: var(--text);
}

.kp-diagram .dg-axis {
    stroke: var(--border-strong);
    stroke-width: 1;
}

.kp-diagram .dg-guide {
    stroke: var(--border-strong);
    stroke-width: 1;
    stroke-dasharray: 3 3;
}

.kp-diagram figcaption {
    font-family: 'Public Sans', sans-serif;
    font-size: .76rem;
    color: var(--text-muted);
    margin-top: 8px;
    border: none;
    padding: 0;
    background: none;
    text-transform: none;
    letter-spacing: 0;
}

/* inline per-key-point check */
.kp-check {
    margin-top: 18px;
    border: 1px solid var(--border);
    border-left: 3px solid var(--gold);
    border-radius: 2px;
    padding: 14px 16px;
    background: var(--bg-raised);
}

.kp-check-head {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .66rem;
    text-transform: uppercase;
    letter-spacing: .08em;
    color: var(--gold);
    margin-bottom: 8px;
}

.kp-check .kp-q {
    font-family: 'Public Sans', sans-serif;
    font-size: .92rem;
    margin: 0 0 12px;
    color: var(--text);
}

.kp-check .option-list {
    gap: 6px;
}

.kp-opt {
    width: 100%;
    text-align: left;
    background: var(--bg);
    color: var(--text);
    font-family: 'Public Sans', sans-serif;
    font-size: .88rem;
    line-height: 1.4;
}

.kp-opt .kp-letter {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .74rem;
    color: var(--text-muted);
    flex: none;
}

.kp-opt.correct .kp-letter,
.kp-opt.incorrect .kp-letter {
    color: inherit;
}

.kp-opt:disabled {
    cursor: default;
    opacity: 1;
}

.kp-check .feedback-box {
    margin-top: 12px;
}

/* the way out, kept deliberately quiet — it is there when wanted, not an invitation */
.kp-check-foot {
    display: flex;
    justify-content: flex-end;
    margin-top: 10px;
    min-height: 14px;
}

.kp-reveal {
    font-family: 'IBM Plex Mono', monospace;
    font-size: .68rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--text-muted);
    background: none;
    border: none;
    padding: 0;
    cursor: pointer;
    text-decoration: underline;
    text-underline-offset: 3px;
}

.kp-reveal:hover {
    color: var(--accent);
}

/* the answer, told rather than earned: outlined, not filled like a correct pick */
.kp-opt.revealed {
    border-color: var(--success);
    border-style: dashed;
    background: transparent;
}

/* closing nudge once every key point is checked */
.kp-done-note {
    margin: 4px 0 0;
    padding: 14px 16px;
    border: 1px dashed var(--success);
    border-radius: 2px;
    background: var(--success-soft);
    color: var(--success);
    font-family: 'Public Sans', sans-serif;
    font-size: .88rem;
}

.kp-done-note.partial {
    border-color: var(--border-strong);
    background: var(--bg-raised);
    color: var(--text-muted);
}

/* distinction card: two sides of something students confuse */
.formula-box.kind-distinction {
    border-left: 3px solid var(--gold);
}

.kp-compare {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: stretch;
    gap: 0;
}

.kp-side {
    padding: 14px 16px;
}

.kp-side p {
    margin: 0;
    font-family: 'Public Sans', sans-serif;
    font-size: .84rem;
    line-height: 1.55;
    color: var(--text-muted);
}

.kp-side-label {
    display: block;
    font-family: 'IBM Plex Mono', monospace;
    font-size: .68rem;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: var(--accent);
    margin-bottom: 6px;
}

.kp-side:last-child .kp-side-label {
    color: var(--gold);
}

.kp-vs {
    align-self: center;
    font-family: 'IBM Plex Mono', monospace;
    font-size: .64rem;
    text-transform: uppercase;
    letter-spacing: .08em;
    color: var(--text-muted);
    padding: 4px 2px;
    border-left: 1px dashed var(--border-strong);
    border-right: 1px dashed var(--border-strong);
    background: var(--bg-sunken);
    writing-mode: vertical-rl;
}

@media (max-width: 720px) {
    .kp-head h3 {
        font-size: 1.25rem;
    }

    .formula-exp {
        font-size: .86rem;
    }

    .kp-compare {
        grid-template-columns: 1fr;
    }

    .kp-vs {
        writing-mode: horizontal-tb;
        text-align: center;
        border-left: none;
        border-right: none;
        border-top: 1px dashed var(--border-strong);
        border-bottom: 1px dashed var(--border-strong);
    }
}

/* sequence card: content whose ORDER is the examinable fact (the adoption path of the
   Code, eliminate-then-safeguard-then-decline). Numbered ticket stubs down the card. */
.formula-box.kind-sequence {
    border-left: 3px solid var(--accent);
}

.kp-steps {
    margin: 0;
    padding: 6px 16px 10px;
    list-style: none;
    counter-reset: kpstep;
}

.kp-steps li {
    counter-increment: kpstep;
    position: relative;
    padding: 9px 0 9px 38px;
    font-family: 'Public Sans', sans-serif;
    font-size: .88rem;
    line-height: 1.55;
    color: var(--text);
    border-bottom: 1px dashed var(--border);
}

.kp-steps li:last-child {
    border-bottom: none;
}

.kp-steps li::before {
    content: counter(kpstep);
    position: absolute;
    left: 0;
    top: 9px;
    width: 22px;
    height: 22px;
    border: 1px solid var(--border-strong);
    border-radius: 50%;
    background: var(--bg);
    font-family: 'IBM Plex Mono', monospace;
    font-size: .7rem;
    line-height: 20px;
    text-align: center;
    color: var(--accent);
}

/* the arrow between steps, drawn on the gap so the order reads as a flow */
.kp-steps li:not(:last-child)::after {
    content: '';
    position: absolute;
    left: 10.5px;
    top: 31px;
    bottom: -1px;
    border-left: 1px dashed var(--border-strong);
}

.formula-exp.kp-steps-note {
    border-top: 1px dashed var(--border-strong);
    font-size: .8rem;
    padding: 12px 16px;
}