/* PSC.FunctionStudy shared stylesheet.
   Ships with the Razor Class Library, so every host (web, MAUI Blazor Hybrid)
   picks it up from _content/PSC.FunctionStudy.UI/app.css. */

:root {
    --ink: #16181d;
    --ink-soft: #565b66;
    --ink-faint: #8b909c;
    --paper: #fbfaf7;
    --card: #ffffff;
    --rule: #e3e0d8;
    --accent: #2f5bd0;
    --accent-soft: #eaf0fe;
    --pos: #1a7f52;
    --neg: #b8451f;
    --curve: #2f5bd0;
    --asym: #b8451f;
    --extremum: #1a7f52;
    --inflection: #8a4fbd;
    --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
    --sans: ui-sans-serif, system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --mono: ui-monospace, "Cascadia Mono", "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --ink: #e9e7e2;
        --ink-soft: #a8adb8;
        --ink-faint: #767b86;
        --paper: #15171b;
        --card: #1c1f25;
        --rule: #2e323a;
        --accent: #7fa4ff;
        --accent-soft: #1e2942;
        --pos: #55c98d;
        --neg: #f08a5f;
        --curve: #7fa4ff;
        --asym: #f08a5f;
        --extremum: #55c98d;
        --inflection: #c08ae8;
    }
}

html { box-sizing: border-box; }
*, *::before, *::after { box-sizing: inherit; }

body {
    margin: 0;
    padding: 0 1.25rem 5rem;
    background: var(--paper);
    color: var(--ink);
    font-family: var(--sans);
    font-size: 16px;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* ---------- masthead ---------- */

.masthead {
    max-width: 46rem;
    margin: 0 auto;
    padding: 3.5rem 0 1.75rem;
}

.eyebrow {
    margin: 0 0 .4rem;
    font-size: .78rem;
    font-weight: 600;
    letter-spacing: .13em;
    text-transform: uppercase;
    color: var(--accent);
}

.masthead h1 {
    margin: 0 0 .6rem;
    font-family: var(--serif);
    font-size: clamp(2rem, 5vw, 2.9rem);
    font-weight: 600;
    line-height: 1.1;
    letter-spacing: -.02em;
}

.lede {
    margin: 0;
    max-width: 38rem;
    color: var(--ink-soft);
    font-size: 1.05rem;
}

/* ---------- input ---------- */

.entry {
    display: flex;
    align-items: center;
    gap: .6rem;
    flex-wrap: wrap;
    max-width: 46rem;
    margin: 0 auto;
    padding: 1rem 1.1rem;
    background: var(--card);
    border: 1px solid var(--rule);
    border-radius: 12px;
}

.entry-label {
    font-family: var(--serif);
    font-size: 1.2rem;
    font-style: italic;
    color: var(--ink-soft);
    white-space: nowrap;
}

.entry-input {
    flex: 1 1 14rem;
    min-width: 0;
    padding: .55rem .7rem;
    background: transparent;
    color: var(--ink);
    border: 1px solid var(--rule);
    border-radius: 7px;
    font-family: var(--mono);
    font-size: 1.02rem;
}

.entry-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-soft);
}

.entry-go {
    padding: .55rem 1.2rem;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: 7px;
    font-family: inherit;
    font-size: .95rem;
    font-weight: 600;
    cursor: pointer;
}

.entry-go:hover { filter: brightness(1.08); }

.samples {
    display: flex;
    align-items: center;
    gap: .4rem;
    flex-wrap: wrap;
    max-width: 46rem;
    margin: .85rem auto 0;
}

.samples-label {
    font-size: .85rem;
    color: var(--ink-faint);
}

.chip {
    padding: .3rem .65rem;
    background: transparent;
    color: var(--ink-soft);
    border: 1px solid var(--rule);
    border-radius: 999px;
    font-family: var(--mono);
    font-size: .82rem;
    cursor: pointer;
}

.chip:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-soft);
}

.error {
    max-width: 46rem;
    margin: 1rem auto 0;
    padding: .7rem .9rem;
    border-left: 3px solid var(--neg);
    background: var(--card);
    color: var(--neg);
    font-size: .93rem;
}

/* ---------- steps ---------- */

.steps {
    max-width: 46rem;
    margin: 2.5rem auto 0;
}

.step {
    position: relative;
    padding: 1.6rem 0;
    border-top: 1px solid var(--rule);
}

.step-no {
    display: block;
    margin-bottom: .3rem;
    font-family: var(--mono);
    font-size: .75rem;
    font-weight: 600;
    letter-spacing: .1em;
    color: var(--ink-faint);
}

.step h2 {
    margin: 0 0 .8rem;
    font-family: var(--serif);
    font-size: 1.35rem;
    font-weight: 600;
    letter-spacing: -.01em;
}

.step p { margin: 0 0 .7rem; }
.step p:last-child { margin-bottom: 0; }

.expr {
    font-family: var(--mono);
    font-size: .97rem;
    font-variant-ligatures: none;
}

/* typeset formulas — MathML, laid out by the browser */

.math-line {
    display: flex;
    align-items: center;
    gap: .5rem;
    margin: 0 0 .9rem;
    overflow-x: auto;   /* a quotient-rule derivative can run very wide */
    overflow-y: hidden; /* ...but never tall enough to need a vertical bar */
    padding-bottom: .3rem;
}

.math-label {
    flex: none;
    font-family: var(--serif);
    font-size: 1.15rem;
    font-style: italic;
    color: var(--ink-soft);
}

.math-line math {
    font-size: 1.25rem;
    color: var(--ink);
}

.result {
    display: inline-block;
    margin-top: .2rem;
    padding: .45rem .8rem;
    background: var(--accent-soft);
    border-radius: 7px;
    color: var(--accent);
    font-weight: 600;
}

/* named-curve callout */

.known {
    margin-top: .8rem;
    padding: .7rem .9rem;
    background: var(--card);
    border: 1px solid var(--rule);
    border-left: 3px solid var(--accent);
    border-radius: 0 8px 8px 0;
}

.known-tag {
    display: inline-block;
    margin-right: .5rem;
    padding: .1rem .45rem;
    vertical-align: 1px;
    background: var(--accent-soft);
    border-radius: 999px;
    color: var(--accent);
    font-size: .7rem;
    font-weight: 600;
    letter-spacing: .06em;
    text-transform: uppercase;
    white-space: nowrap;
}

.conds, .limits, .points {
    margin: 0 0 .8rem;
    padding-left: 1.2rem;
}

.conds li, .limits li, .points li { margin: .25rem 0; }

/* ---------- sign / monotonicity / concavity charts ---------- */

.chart {
    width: 100%;
    margin: .5rem 0 1rem;
    border-collapse: collapse;
    font-size: .93rem;
}

.chart td {
    padding: .45rem .7rem;
    border-bottom: 1px solid var(--rule);
    vertical-align: top;
}

.chart td:first-child { white-space: nowrap; color: var(--ink-soft); }

.sign.pos { color: var(--pos); }
.sign.neg { color: var(--neg); }
.sign.zero { color: var(--ink-faint); }

/* ---------- asymptotes ---------- */

.asyms { margin: 0; }

.asyms dt {
    display: flex;
    align-items: center;
    gap: .55rem;
    margin-top: .7rem;
    font-weight: 600;
}

.asyms dd {
    margin: .15rem 0 0;
    color: var(--ink-soft);
    font-family: var(--mono);
    font-size: .85rem;
}

.tag {
    padding: .1rem .45rem;
    background: var(--accent-soft);
    border-radius: 999px;
    color: var(--accent);
    font-family: var(--sans);
    font-size: .7rem;
    font-weight: 600;
    letter-spacing: .06em;
    text-transform: uppercase;
}

/* ---------- plot ---------- */

.plot { margin-top: .5rem; }

.plot-toolbar {
    display: flex;
    align-items: center;
    gap: .35rem;
    flex-wrap: wrap;
    margin-bottom: .6rem;
}

.plot-window {
    margin-left: auto;
    color: var(--ink-faint);
    font-family: var(--mono);
    font-size: .78rem;
}

.plot-svg {
    display: block;
    width: 100%;
    height: auto;
    background: var(--card);
    border: 1px solid var(--rule);
    border-radius: 10px;
}

.grid { stroke: var(--rule); stroke-width: 1; }
.axis { stroke: var(--ink-faint); stroke-width: 1.4; }
.tick { fill: var(--ink-faint); font-family: var(--mono); font-size: 11px; }

.curve {
    fill: none;
    stroke: var(--curve);
    stroke-width: 2.2;
    stroke-linecap: round;
    stroke-linejoin: round;
}

.asym {
    stroke: var(--asym);
    stroke-width: 1.5;
    stroke-dasharray: 6 5;
}

.mark { stroke: var(--card); stroke-width: 2; }
.mark.extremum { fill: var(--extremum); }
.mark.inflection { fill: var(--inflection); }

.mark-label {
    fill: var(--ink-soft);
    font-family: var(--mono);
    font-size: 11px;
}

.legend {
    display: flex;
    gap: 1.1rem;
    flex-wrap: wrap;
    margin: .6rem 0 0;
    padding: 0;
    list-style: none;
    color: var(--ink-soft);
    font-size: .82rem;
}

.legend li { display: flex; align-items: center; gap: .4rem; }

.swatch {
    width: 15px;
    height: 3px;
    border-radius: 2px;
}

.curve-swatch { background: var(--curve); }

.asym-swatch {
    background: repeating-linear-gradient(90deg, var(--asym) 0 5px, transparent 5px 9px);
}

.mark-swatch { width: 9px; height: 9px; border-radius: 50%; }
.mark-swatch.extremum { background: var(--extremum); }
.mark-swatch.inflection { background: var(--inflection); }

/* FocusOnNavigate moves focus to the h1 on every navigation so a screen reader announces the
   new page. That is worth keeping, but the heading was focused programmatically rather than
   tabbed to, so the ring reads as a rendering fault. Scoped to headings, which are never
   interactive, so no keyboard affordance is lost. */
h1[tabindex="-1"]:focus { outline: none; }

/* ---------- method guide ---------- */

/* the step boxes are already position: relative, so this tucks into the top-right corner */
.step-help {
    position: absolute;
    top: 1.6rem;
    right: 0;
    color: var(--ink-faint);
    font-size: .78rem;
    text-decoration: none;
    white-space: nowrap;
}

.step-help:hover,
.step-help:focus-visible {
    color: var(--accent);
    text-decoration: underline;
}

.back-link {
    color: var(--ink-soft);
    font-size: .9rem;
    text-decoration: none;
}

.back-link:hover { color: var(--accent); }

.method-index {
    max-width: 46rem;
    margin: 0 auto;
    padding: 0;
    list-style: none;
    counter-reset: none;
}

.method-index li { border-top: 1px solid var(--rule); }

.method-index a {
    display: grid;
    grid-template-columns: 3rem 1fr;
    gap: .1rem .6rem;
    padding: 1rem .6rem 1rem 0;
    color: inherit;
    text-decoration: none;
}

.method-index a:hover,
.method-index a:focus-visible {
    background: var(--accent-soft);
}

.method-index .step-no { grid-row: span 2; padding-top: .15rem; }

.method-index strong {
    font-family: var(--serif);
    font-size: 1.15rem;
    font-weight: 600;
}

.method-question { color: var(--ink-soft); font-size: .92rem; }

.reading { margin: 0; padding-left: 1.2rem; }

.reading li { margin: .45rem 0; }

.reading a {
    color: var(--accent);
    text-decoration: none;
    border-bottom: 1px solid transparent;
}

.reading a:hover,
.reading a:focus-visible { border-bottom-color: var(--accent); }

.reading-source {
    margin-left: .45rem;
    color: var(--ink-faint);
    font-size: .8rem;
}

.method-nav {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    max-width: 46rem;
    margin: 2rem auto 0;
    padding-top: 1.2rem;
    border-top: 1px solid var(--rule);
    font-size: .9rem;
}

.method-nav a { color: var(--ink-soft); text-decoration: none; }
.method-nav a:hover { color: var(--accent); }
.method-nav .method-next { margin-left: auto; text-align: right; }

/* ---------- footer ---------- */

.site-footer {
    max-width: 46rem;
    margin: 4rem auto 0;
    padding-top: 1.4rem;
    border-top: 1px solid var(--rule);
    font-size: .85rem;
}

.footer-group {
    display: flex;
    align-items: baseline;
    flex-wrap: wrap;
    gap: .3rem 1rem;
}

.footer-group + .footer-group {
    margin-top: .55rem;
}

.footer-label {
    color: var(--ink-faint);
}

.site-footer a {
    color: var(--ink-soft);
    text-decoration: none;
    border-bottom: 1px solid transparent;
}

.site-footer a:hover,
.site-footer a:focus-visible {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

/* ---------- framework error bar ---------- */

#blazor-error-ui {
    display: none;
    position: fixed;
    left: 0;
    bottom: 0;
    z-index: 1000;
    width: 100%;
    padding: .7rem 1.25rem;
    background: #ffeaa7;
    color: #3a2f00;
    box-shadow: 0 -1px 3px rgba(0, 0, 0, .2);
}

#blazor-error-ui .dismiss {
    position: absolute;
    top: .55rem;
    right: 1rem;
    cursor: pointer;
}