/* Knit landing page.
 *
 * The whole page is built from the logo's own colors (extracted from
 * knit-logo-dark.svg) so the site and the brand match. Colors are defined once
 * here as custom properties and reused throughout (buttons, accents, and, in a
 * later milestone, the code theme). */

:root {
    /* Brand palette (from knit-logo-dark.svg). */
    --knit-purple: #9e7fd4;   /* dominant  -> primary accent / builtins   */
    --knit-coral: #fe8369;    /* secondary -> accents / strings           */
    --knit-magenta: #b83a83;  /* accent    -> literals                    */
    --knit-deep: #684675;     /* shadow    -> muted borders / comments    */
    --knit-white: #ffffff;

    /* Page surfaces. */
    --knit-bg: #0d1117;             /* near-black canvas suiting the dark logo */
    --knit-surface: #161b26;       /* cards: a touch lighter than the canvas   */
    --knit-border: rgba(104, 70, 117, 0.45); /* muted deep-purple hairline     */
    --knit-fg: #e8e6ef;            /* body text: soft white, not pure #fff     */
    --knit-fg-muted: #a89fc0;      /* secondary text: dimmed purple-grey       */
}

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

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    background-color: var(--knit-bg);
    color: var(--knit-fg);
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial,
        sans-serif;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* -- Hero ------------------------------------------------------------------ */

.hero {
    position: relative;
    min-height: 100vh;
    min-height: 100svh; /* avoids the mobile URL-bar jump where supported */
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2.5rem;
    padding: 2rem 1.5rem 6rem;
    text-align: center;
}

.hero__logo {
    width: min(840px, 90vw);
    height: auto;
    /* A soft brand-tinted glow so the logo sits on the dark canvas. */
    filter: drop-shadow(0 12px 40px rgba(158, 127, 212, 0.25));
}

.hero__actions {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: 1rem;
}

/* -- Buttons --------------------------------------------------------------- */

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.6em;
    padding: 0.75rem 1.5rem;
    border-radius: 0.6rem;
    border: 2px solid transparent;
    font-size: 1.05rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: transform 0.15s ease, background-color 0.15s ease,
        border-color 0.15s ease, color 0.15s ease, box-shadow 0.15s ease;
}

.btn:hover {
    transform: translateY(-2px);
}

.btn:focus-visible {
    outline: 3px solid var(--knit-coral);
    outline-offset: 3px;
}

.btn .fa-book,
.btn .fa-github {
    font-size: 1.05em;
}

/* Primary: filled brand purple. */
.btn--primary {
    background-color: var(--knit-purple);
    color: #1a1226;
    border-color: var(--knit-purple);
}

.btn--primary:hover {
    background-color: #b199e0;
    border-color: #b199e0;
    box-shadow: 0 8px 24px rgba(158, 127, 212, 0.35);
}

/* Secondary: outlined. */
.btn--secondary {
    background-color: transparent;
    color: var(--knit-fg);
    border-color: var(--knit-deep);
}

.btn--secondary:hover {
    border-color: var(--knit-purple);
    color: var(--knit-white);
    box-shadow: 0 8px 24px rgba(104, 70, 117, 0.35);
}

/* -- Scroll cue ------------------------------------------------------------ */

.hero__scroll-cue {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    color: var(--knit-fg-muted);
    font-size: 1.5rem;
    text-decoration: none;
    animation: knit-bob 2s ease-in-out infinite;
    transition: color 0.15s ease;
}

.hero__scroll-cue:hover {
    color: var(--knit-coral);
}

@keyframes knit-bob {
    0%, 100% { transform: translate(-50%, 0); }
    50%      { transform: translate(-50%, 8px); }
}

/* -- Scroll narrative: sections ------------------------------------------- */

.section {
    padding: clamp(2rem, 6vh, 4.5rem) 1.5rem;
}

.section:nth-of-type(odd) {
    /* Alternate a subtly raised band to separate consecutive sections. The first
       section is odd, so it starts on the lighter shade — distinct from the hero
       above it. */
    background-color: rgba(255, 255, 255, 0.015);
}

.section__inner {
    max-width: 820px;
    margin: 0 auto;
}

.section__title {
    margin: 0 0 0.75rem;
    font-size: clamp(1.5rem, 3.5vw, 2.1rem);
    line-height: 1.2;
    color: var(--knit-white);
}

.section__lead {
    margin: 0 0 2rem;
    font-size: 1.1rem;
    color: var(--knit-fg-muted);
}

/* The five-stage flow diagram (arrow SVG) introducing the model. */
.section__diagram {
    margin: 0 0 2rem;
}

.section__diagram img {
    display: block;
    width: 100%;
    height: auto;
}

.section--cta {
    text-align: center;
}

.section--cta .hero__actions {
    margin-top: 1.5rem;
}

/* Inline code inside prose. */
.section__lead code {
    padding: 0.1em 0.4em;
    border-radius: 0.3rem;
    background-color: rgba(158, 127, 212, 0.14);
    color: var(--knit-purple);
    font-size: 0.9em;
}

/* -- Cards (code snippets and terminal transcripts) ----------------------- */

.card {
    margin: 1.25rem 0 0;
    border: 1px solid var(--knit-border);
    border-radius: 0.7rem;
    background-color: var(--knit-surface);
    overflow: hidden;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
}

.card__head {
    padding: 0.5rem 1rem;
    border-bottom: 1px solid var(--knit-border);
    background-color: rgba(0, 0, 0, 0.2);
    font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    font-size: 0.8rem;
    color: var(--knit-fg-muted);
}

/* Terminal header: three "traffic light" dots instead of a filename. */
.card__head--term {
    display: flex;
    gap: 0.45rem;
    align-items: center;
}

.card__head--term .dot {
    width: 0.7rem;
    height: 0.7rem;
    border-radius: 50%;
    background-color: var(--knit-deep);
}

.card__head--term .dot:nth-child(1) { background-color: var(--knit-coral); }
.card__head--term .dot:nth-child(2) { background-color: var(--knit-purple); }
.card__head--term .dot:nth-child(3) { background-color: var(--knit-magenta); }

.card__body {
    margin: 0;
    padding: 1rem 1.25rem;
    overflow-x: auto;
    font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    font-size: 0.9rem;
    line-height: 1.55;
    color: var(--knit-fg);
    white-space: pre;
    tab-size: 4;
}

/* A terminal command line: a colored prompt, not part of the copied text
   selection start, and a slightly brighter foreground. */
.card--term .cmd {
    color: var(--knit-white);
    font-weight: 600;
}

.card--term .cmd::before {
    content: "$ ";
    color: var(--knit-coral);
    font-weight: 700;
}

.card--term .comment {
    color: var(--knit-fg-muted);
    font-style: italic;
}

/* -- Scroll reveal --------------------------------------------------------- */

/* Only hide-then-reveal when JS is present (the `js` class is set inline in the
   <head>); without JS every section stays visible. */
.js .reveal {
    opacity: 0;
    transform: translateY(28px);
    transition: opacity 0.6s ease, transform 0.6s ease;
    will-change: opacity, transform;
}

.js .reveal.is-visible {
    opacity: 1;
    transform: none;
}

/* -- Footer ---------------------------------------------------------------- */

.site-footer {
    padding: 2rem 1.5rem 3rem;
    text-align: center;
    border-top: 1px solid var(--knit-border);
    color: var(--knit-fg-muted);
    font-size: 0.9rem;
}

.site-footer p {
    margin: 0;
}

.site-footer a {
    color: var(--knit-purple);
    text-decoration: none;
    transition: color 0.15s ease;
}

.site-footer a:hover {
    color: var(--knit-coral);
    text-decoration: underline;
}

.site-footer a:focus-visible {
    outline: 3px solid var(--knit-coral);
    outline-offset: 3px;
}

/* -- Small screens --------------------------------------------------------- */

/* The layout is fluid by default (clamp() padding/titles, min() logo, wrapping
   button row, horizontally scrollable card bodies). These are just comfort
   tweaks so nothing feels cramped on a phone. */
@media (max-width: 520px) {
    .hero {
        gap: 1.75rem;
    }

    /* Slightly smaller code so the widest transcript lines need less sideways
       scrolling on a narrow viewport. */
    .card__body {
        font-size: 0.82rem;
        padding: 0.9rem 1rem;
    }

    .hero__actions {
        /* Let the two buttons stack full-width rather than crowd side by side. */
        width: 100%;
    }

    .hero__actions .btn {
        flex: 1 1 100%;
        justify-content: center;
    }
}

/* -- Reduced motion -------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    .hero__scroll-cue {
        animation: none;
    }

    .btn:hover {
        transform: none;
    }

    /* Show revealed content immediately, with no transition. */
    .js .reveal {
        opacity: 1;
        transform: none;
        transition: none;
    }
}