/* Shared look of the step-by-step animations (anim.js). */
:root {
    --paper: #f3eee3;
    --panel: #fffcf5;
    --ink: #26221c;
    --muted: #786f61;
    --line: #ddd3c1;
    --inline-code: #ece5d6;

    --code-bg: #22252f;
    --code-ink: #e9e6dd;
    --code-num: #6c7285;
    --code-active: #363d52;
    --code-marker: #ffd166;

    --name-bg: #c4e3b8;
    --name-border: #4f8a45;
    --name-ink: #18330f;
    --obj-bg: #fff3cf;
    --obj-border: #c99a2e;
    --gone-bg: #efe9dc;
    --gone-border: #cfc4af;

    --read: #2563c9;
    --read-bg: #dbe7fb;
    --write: #d66d08;
    --write-bg: #fde5c8;
    --err: #c4302b;
    --err-bg: #f9d9d6;
    --ref: #7b48c4;
    --ok: #3f8a3a;

    --mono: "JetBrains Mono", "Fira Code", "Cascadia Code", Consolas, "DejaVu Sans Mono", monospace;
    --sans: "Segoe UI", "Noto Sans", Roboto, "Helvetica Neue", Arial, sans-serif;

    /* The unit of a memory diagram (names, objects, frames, arrows): 1rem, but it
       does not stop at 22px - on a big screen the diagram fills the same share of
       its panel. A page scales it (--k) and caps it by the panel width (--u). */
    --dia: max(1rem, min(1.15vw, 2.05vh));
}
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --paper: #17181d; --panel: #202229; --ink: #ecebe6; --muted: #9a988f; --line: #363945; --inline-code: #2d3039;
        --code-bg: #111318; --code-active: #2c3345;
        --name-bg: #2c4a2a; --name-border: #71b066; --name-ink: #d8f3cf;
        --obj-bg: #3a3220; --obj-border: #c9a24a;
        --gone-bg: #262830; --gone-border: #3d404c;
        --read: #6ea2ff; --read-bg: #1f3354; --write: #ffa24d; --write-bg: #4a2e12;
        --err: #ff6b63; --err-bg: #4a1c1a; --ref: #b38cff; --ok: #7fd17a;
    }
}
:root[data-theme="dark"] {
    --paper: #17181d; --panel: #202229; --ink: #ecebe6; --muted: #9a988f; --line: #363945; --inline-code: #2d3039;
    --code-bg: #111318; --code-active: #2c3345;
    --name-bg: #2c4a2a; --name-border: #71b066; --name-ink: #d8f3cf;
    --obj-bg: #3a3220; --obj-border: #c9a24a;
    --gone-bg: #262830; --gone-border: #3d404c;
    --read: #6ea2ff; --read-bg: #1f3354; --write: #ffa24d; --write-bg: #4a2e12;
    --err: #ff6b63; --err-bg: #4a1c1a; --ref: #b38cff; --ok: #7fd17a;
}

* { box-sizing: border-box; }
html { font-size: clamp(11px, min(1.15vw, 2.05vh), 22px); }
body {
    margin: 0;
    min-height: 100vh;
    background: var(--paper);
    color: var(--ink);
    font-family: var(--sans);
}
.app {
    display: grid;
    grid-template-rows: auto minmax(0, 1fr) auto;
    gap: .7rem;
    height: 100vh;
    padding: .8rem 1rem;
}

/* ---------- header ---------- */
.top { display: flex; align-items: center; gap: 1.2rem; }
.top h1 { margin: 0; font-size: 1.35rem; font-weight: 750; letter-spacing: -.01em; white-space: nowrap; }
.top h1 small { display: block; font-size: .7rem; font-weight: 500; color: var(--muted); letter-spacing: 0; }
.tabs { display: flex; flex-wrap: wrap; gap: .35rem; flex: 1; }
.tab {
    font: inherit; font-size: .82rem;
    padding: .38rem .8rem;
    border: 1px solid var(--line); border-radius: 999px;
    background: var(--panel); color: var(--ink);
    cursor: pointer;
}
.tab:hover { border-color: var(--muted); }
.tab[aria-selected="true"] { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.tab .adv { font-size: .65rem; font-weight: 700; color: var(--ref); margin-left: .3rem; }
.tab[aria-selected="true"] .adv { color: inherit; opacity: .75; }
.tab code { font-family: var(--mono); font-size: .9em; }

/* ---------- panels ---------- */
.stage { min-height: 0; }
.panel {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: .6rem;
    padding: .6rem .8rem;
    min-height: 0;
}
.panel-title {
    display: flex; justify-content: space-between; gap: 1rem;
    margin-bottom: .45rem;
    font-size: .7rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase;
    color: var(--muted);
}

/* code */
.code-panel { background: var(--code-bg); border-color: var(--line); }
.code-panel .panel-title { color: var(--code-num); }
.code { list-style: none; margin: 0; padding: 0; font-family: var(--mono); font-size: 1.02rem; }
.code li {
    display: flex; gap: .8rem;
    padding: .2rem .5rem;
    border-left: 3px solid transparent; border-radius: .25rem;
    color: var(--code-ink);
    white-space: pre;
    transition: background .25s;
}
.code .ln { flex: none; width: 1.2rem; text-align: right; color: var(--code-num); }
.code li.active { background: var(--code-active); border-left-color: var(--code-marker); }
.code li.active.error { background: #4d2329; border-left-color: #ff6b63; }
.code li.done { opacity: .75; }
.hl-k { color: #c792ea; }
.hl-s { color: #a5d986; }
.hl-n { color: #f7b267; }
.hl-c { color: #7a8299; font-style: italic; }
.hl-b { color: #82aaff; }

/* console */
.console { font-family: var(--mono); font-size: .98rem; overflow: auto; }
.cline { padding: .15rem .4rem; border-bottom: 1px solid var(--line); white-space: pre-wrap; }
.cline.err { color: var(--err); background: var(--err-bg); }
.cline.new { animation: pop .45s ease-out; }
.empty { font-size: .8rem; color: var(--muted); font-style: italic; }

/* ---------- footer: explanation and controls ---------- */
.bottom { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 1rem; align-items: center; }
.explain {
    min-height: 4.6rem;
    padding: .7rem 1rem;
    border: 1px solid var(--line); border-left: 4px solid var(--write);
    border-radius: .6rem;
    background: var(--panel);
    font-size: 1.02rem; line-height: 1.5;
}
.explain code { font-family: var(--mono); font-size: .92em; padding: 0 .25rem; border-radius: .25rem; background: var(--inline-code); }
.controls { display: flex; align-items: center; gap: .4rem; }
.btn {
    display: inline-flex; align-items: center; gap: .35rem;
    font: inherit; font-size: .85rem; font-weight: 600;
    padding: .45rem .8rem;
    border: 1px solid var(--line); border-radius: .5rem;
    background: var(--panel); color: var(--ink);
    cursor: pointer; text-decoration: none;
}
.btn:hover { border-color: var(--muted); }
.btn:disabled { opacity: .4; cursor: default; }
.btn.primary { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.btn svg { width: .9rem; height: .9rem; fill: currentColor; }
.icon-btn { padding: .45rem .55rem; }
.counter { min-width: 4.5rem; text-align: center; font-size: .8rem; color: var(--muted); font-variant-numeric: tabular-nums; }
.lang-btn { font-weight: 700; font-size: .8rem; letter-spacing: .04em; }

/* going back or jumping: no entry animations */
.static .hl-new, .static .new, .static .draw { animation: none !important; }
.static path.draw { stroke-dasharray: none; stroke-dashoffset: 0; }

@keyframes pop { from { transform: scale(.85); opacity: 0; } to { transform: none; opacity: 1; } }
@keyframes shake { 0%, 100% { transform: none; } 25% { transform: translateX(-4px); } 75% { transform: translateX(4px); } }
@media (prefers-reduced-motion: reduce) { * { animation: none !important; transition: none !important; } }

@media (max-width: 760px) {
    html { font-size: 13px; }
    .app { height: auto; }
    .top { flex-wrap: wrap; }
    .top h1 { white-space: normal; }
    /* a phone: the panels one below the other (body: stronger than the page's .stage),
       and a long code line scrolls inside its panel, not the whole page */
    body .stage { grid-template-columns: minmax(0, 1fr); }
    .left, .col { grid-template-columns: minmax(0, 1fr); }
    .code-panel { overflow-x: auto; }
    .code { min-width: max-content; }
    .bottom { grid-template-columns: 1fr; }
}