@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;700&display=swap');

/* ── ROOT ──────────────────────────────────────────────── */
:root {
    --bg: #030f0a;
    --panel: rgba(5, 20, 12, 0.9);
    --border: rgba(255,255,255,0.07);
    --green: #10b981;
    --green-lt: #34d399;
    --green-glow: rgba(16,185,129,0.15);
    --teal: #06b6d4;
    --amber: #f59e0b;
    --purple: #a855f7;
    --red: #f87171;
    --blue: #3b82f6;
    --text: #f1f5f9;
    --muted: #64748b;
    --atom-C: #4b5563;
    --atom-H: #d1d5db;
    --atom-O: #ef4444;
    --atom-N: #3b82f6;
    --atom-Cl: #16a34a;
}
* { box-sizing:border-box; margin:0; padding:0; }

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
}

body.iso-page {
    font-family:'Outfit', sans-serif;
    background:var(--bg);
    color:var(--text);
    touch-action: none;
    overscroll-behavior: none;
}

/* PhET Stage — scalable wrapper */
#phet-stage {
    position: absolute;
    top: 0;
    left: 0;
    transform-origin: top left;
    overflow-y: auto;
    overflow-x: hidden;
    /* background carries through from body */
    background:var(--bg);
}

body.iso-page::before {
    content:''; position:fixed; inset:0;
    background:
        radial-gradient(ellipse 65% 55% at 10% 20%, rgba(16,185,129,0.07) 0%, transparent 65%),
        radial-gradient(ellipse 55% 55% at 90% 75%, rgba(6,182,212,0.05) 0%, transparent 65%);
    pointer-events:none; z-index:0;
}

/* ── NAV ───────────────────────────────────────────────── */
.iso-nav {
    position:fixed; top:0; left:0; right:0; z-index:300;
    display:flex; align-items:center; justify-content:space-between;
    padding:0.55rem 1.4rem;
    background:rgba(3,15,10,0.92); backdrop-filter:blur(16px);
    border-bottom:1px solid var(--border);
}
.iso-nav .logo { font-size:1rem; font-weight:800; }
.nav-crumb { font-size:0.78rem; color:#94a3b8; display:flex; align-items:center; gap:0.5rem; }
.nav-crumb strong { color:var(--text); }
.crumb-sep { opacity:0.25; }
.nav-right { display:flex; gap:0.6rem; align-items:center; }
.info-nav-btn {
    background:rgba(16,185,129,0.12); border:1px solid rgba(16,185,129,0.3);
    color:var(--green); padding:0.32rem 0.9rem; border-radius:50px;
    font-size:0.78rem; font-weight:700; cursor:pointer;
    display:flex; align-items:center; gap:0.4rem; transition:0.2s; font-family:inherit;
}
.info-nav-btn:hover { background:var(--green); color:#030f0a; }
.back-btn {
    border-radius:50px; padding:0.32rem 0.9rem; font-size:0.78rem;
    color:#94a3b8; border:1px solid rgba(255,255,255,0.1);
    text-decoration:none; display:flex; align-items:center; gap:0.4rem; transition:0.2s;
}
.back-btn:hover { border-color:var(--green); color:var(--green); }

/* ── MAIN ───────────────────────────────────────────────── */
.iso-main {
    padding:62px 12px 20px; min-height:100vh;
    display:flex; flex-direction:column; gap:0.6rem; position:relative; z-index:1;
}

/* ── TOP BANNER ─────────────────────────────────────────── */
.top-banner {
    background:linear-gradient(135deg, rgba(5,20,12,0.95), rgba(16,185,129,0.05));
    border:1px solid rgba(16,185,129,0.18); border-radius:14px;
    padding:0.65rem 1.1rem; display:flex; flex-direction:column; gap:0.5rem;
}
.banner-row { display:flex; align-items:center; gap:0.65rem; flex-wrap:wrap; }
.isomer-type-row { display:flex; align-items:center; gap:0.65rem; flex-wrap:wrap; }
.label-sm {
    font-size:0.68rem; font-weight:700; color:var(--muted);
    text-transform:uppercase; letter-spacing:0.5px; flex-shrink:0;
}
.compound-pills, .type-pills { display:flex; gap:0.35rem; flex-wrap:wrap; }
.cpd-pill, .type-pill {
    background:rgba(255,255,255,0.04); border:1px solid var(--border);
    color:var(--muted); padding:0.26rem 0.7rem; border-radius:30px;
    font-size:0.7rem; font-weight:700; cursor:pointer; transition:0.2s; font-family:inherit;
}
.cpd-pill:hover { border-color:var(--green); color:var(--green); }
.cpd-pill.active { background:rgba(16,185,129,0.15); border-color:var(--green); color:var(--green); }
.type-pill:hover { border-color:var(--teal); color:var(--teal); }
.type-pill.active { background:rgba(6,182,212,0.12); border-color:var(--teal); color:var(--teal); }
.formula-badge {
    margin-left:auto; background:rgba(16,185,129,0.1); border:1px solid rgba(16,185,129,0.25);
    color:var(--green); padding:0.18rem 0.65rem; border-radius:20px;
    font-size:0.75rem; font-family:'JetBrains Mono',monospace; font-weight:700;
}

/* ── LAYOUT ─────────────────────────────────────────────── */
.iso-layout {
    display:grid; grid-template-columns:220px 1fr 220px;
    gap:0.65rem; align-items:start;
}
.iso-sidebar, .iso-readings { display:flex; flex-direction:column; }
.iso-center { display:flex; flex-direction:column; }

/* ── PANEL ──────────────────────────────────────────────── */
.panel-box {
    background:var(--panel); border:1px solid var(--border);
    border-radius:13px; padding:0.8rem 0.9rem;
    backdrop-filter:blur(12px); margin-bottom:0.55rem;
}
.panel-title {
    font-size:0.7rem; font-weight:800; text-transform:uppercase;
    letter-spacing:0.7px; color:var(--muted);
    display:flex; align-items:center; gap:0.4rem; margin-bottom:0.55rem;
}
.iso-def {
    font-size:0.74rem; color:#94a3b8; line-height:1.65;
}
.iso-def strong { color:var(--green); }
.iso-def em { color:var(--teal); font-style:normal; font-weight:700; }

/* ── EXPLAIN CARD ───────────────────────────────────────── */
.explain-card {
    background:linear-gradient(135deg, rgba(5,20,12,0.95), rgba(16,185,129,0.06));
    border:1px solid rgba(16,185,129,0.22); border-radius:13px;
    padding:0.9rem; text-align:center; margin-bottom:0.55rem;
}
.ex-icon  { font-size:2rem; margin-bottom:0.3rem; }
.ex-type  { font-size:0.88rem; font-weight:800; color:var(--green); margin-bottom:0.3rem; }
.ex-body  { font-size:0.72rem; color:#94a3b8; line-height:1.6; }
.ex-body strong { color:var(--text); }

/* ── PROPERTIES TABLE ───────────────────────────────────── */
.props-table { display:flex; flex-direction:column; gap:0; }
.props-header {
    display:grid; gap:0.3rem; font-size:0.62rem; font-weight:800;
    color:var(--muted); text-transform:uppercase; letter-spacing:0.3px;
    padding:0.28rem 0.4rem;
    border-bottom:1px solid rgba(255,255,255,0.06);
}
.props-row {
    display:grid; gap:0.3rem; font-size:0.7rem;
    padding:0.32rem 0.4rem; border-bottom:1px solid rgba(255,255,255,0.03);
    align-items:center;
}
.props-cell { overflow:hidden; text-overflow:ellipsis; white-space:nowrap; }
.prop-lbl { color:var(--muted); font-size:0.65rem; }
.prop-val { font-family:'JetBrains Mono',monospace; color:var(--text); font-weight:700; }
.prop-diff { color:var(--amber); }

/* ── CENTER ─────────────────────────────────────────────── */
.center-header { margin-bottom:0.7rem; }
.ch-title { font-size:1.1rem; font-weight:800; color:var(--text); margin-bottom:0.2rem; }
.ch-subtitle { font-size:0.75rem; color:#94a3b8; }

/* ── ISOMER GRID ────────────────────────────────────────── */
.isomer-grid {
    display:grid;
    grid-template-columns:repeat(auto-fill, minmax(260px, 1fr));
    gap:0.7rem;
    margin-bottom:0.7rem;
}
.isomer-card {
    background:var(--panel); border:1px solid var(--border);
    border-radius:14px; padding:0.8rem;
    backdrop-filter:blur(12px);
    transition:border-color 0.2s, box-shadow 0.2s;
    cursor:default;
}
.isomer-card:hover {
    border-color:rgba(16,185,129,0.35);
    box-shadow:0 4px 24px rgba(16,185,129,0.1);
}
.isomer-card.highlighted {
    border-color:rgba(16,185,129,0.5);
    box-shadow:0 0 0 2px rgba(16,185,129,0.15);
}
.ic-header {
    display:flex; align-items:center; justify-content:space-between;
    margin-bottom:0.55rem;
}
.ic-name { font-size:0.82rem; font-weight:800; color:var(--text); }
.ic-iupac { font-size:0.63rem; color:var(--muted); font-style:italic; }
.ic-badge {
    font-size:0.6rem; font-weight:800; padding:0.12rem 0.45rem;
    border-radius:20px; flex-shrink:0;
}
.badge-chain { background:rgba(16,185,129,0.12);color:var(--green);border:1px solid rgba(16,185,129,0.2); }
.badge-position { background:rgba(6,182,212,0.12);color:var(--teal);border:1px solid rgba(6,182,212,0.2); }
.badge-functional { background:rgba(168,85,247,0.12);color:var(--purple);border:1px solid rgba(168,85,247,0.2); }
.badge-ez { background:rgba(245,158,11,0.12);color:var(--amber);border:1px solid rgba(245,158,11,0.2); }
.badge-optical { background:rgba(248,113,113,0.12);color:var(--red);border:1px solid rgba(248,113,113,0.2); }

/* ── MOLECULE CANVAS ────────────────────────────────────── */
.ic-canvas-wrap {
    background:rgba(2,8,5,0.7); border-radius:10px; overflow:hidden;
    margin-bottom:0.5rem; border:1px solid rgba(255,255,255,0.05);
}
.molecule-canvas { display:block; width:100%; height:auto; }
.ic-formula {
    font-family:'JetBrains Mono',monospace; font-size:0.72rem;
    color:var(--green); margin-bottom:0.35rem;
}
.ic-note { font-size:0.68rem; color:#94a3b8; line-height:1.5; }
.ic-note strong { color:var(--text); }

/* ── HIGHLIGHT DIFFERENCES ──────────────────────────────── */
.ic-diff-row {
    display:flex; align-items:center; gap:0.35rem;
    margin-top:0.4rem; padding-top:0.4rem;
    border-top:1px solid rgba(255,255,255,0.05);
}
.ic-diff-label { font-size:0.62rem; color:var(--muted); flex:1; }
.ic-diff-val {
    font-size:0.68rem; font-weight:700; font-family:'JetBrains Mono',monospace;
}

/* ── KEY DIFF BAR ───────────────────────────────────────── */
.key-diff-bar {
    background:linear-gradient(135deg, rgba(5,20,12,0.92), rgba(16,185,129,0.06));
    border:1px solid rgba(16,185,129,0.2); border-radius:12px;
    padding:0.65rem 1rem; display:flex; align-items:center; gap:0.7rem;
}
.kd-icon { font-size:1.3rem; flex-shrink:0; }
.kd-text { font-size:0.76rem; color:#94a3b8; line-height:1.55; }
.kd-text strong { color:var(--green); }

/* ── ISOMERISM TREE ─────────────────────────────────────── */
.iso-tree { font-size:0.72rem; }
.tree-root {
    text-align:center; font-weight:800; color:var(--green);
    padding:0.35rem 0.6rem; border:1px solid rgba(16,185,129,0.3);
    border-radius:8px; margin-bottom:0.5rem;
    background:rgba(16,185,129,0.07);
}
.tree-branch { margin-bottom:0.6rem; }
.tree-node {
    font-weight:800; padding:0.28rem 0.6rem; border-radius:7px;
    margin-bottom:0.3rem; font-size:0.7rem;
}
.tree-node.structural { background:rgba(6,182,212,0.1);color:var(--teal);border:1px solid rgba(6,182,212,0.2); }
.tree-node.stereo { background:rgba(168,85,247,0.1);color:var(--purple);border:1px solid rgba(168,85,247,0.2); }
.tree-children { padding-left:1rem; display:flex; flex-direction:column; gap:0.2rem; }
.tree-leaf {
    font-size:0.68rem; color:#94a3b8; padding:0.18rem 0.5rem;
    border-left:2px solid rgba(255,255,255,0.08); cursor:help;
    transition:color 0.2s;
}
.tree-leaf:hover { color:var(--text); border-left-color:var(--green); }

/* ── RULES ──────────────────────────────────────────────── */
.rules-list { display:flex; flex-direction:column; gap:0.4rem; }
.rule-item { display:flex; gap:0.5rem; align-items:flex-start; font-size:0.7rem; }
.rule-num {
    background:rgba(16,185,129,0.12); color:var(--green);
    border-radius:50%; width:18px; height:18px; min-width:18px;
    display:flex; align-items:center; justify-content:center; font-weight:800; font-size:0.6rem;
}
.rule-text { color:#94a3b8; line-height:1.5; }
.rule-text strong { color:var(--text); }

/* ── MIRROR EFFECT (optical) ────────────────────────────── */
.mirror-pair {
    display:flex; align-items:center; justify-content:center; gap:0.5rem;
    padding:0.4rem; background:rgba(248,113,113,0.04);
    border-radius:8px; border:1px dashed rgba(248,113,113,0.2);
}
.mirror-line {
    width:2px; height:100px; background:rgba(248,113,113,0.35);
    flex-shrink:0; position:relative;
}
.mirror-line::before {
    content:'mirror'; position:absolute; top:-14px; left:50%; transform:translateX(-50%);
    font-size:0.55rem; color:rgba(248,113,113,0.5); white-space:nowrap; letter-spacing:0.5px;
}

/* ── MODAL ──────────────────────────────────────────────── */
.modal-overlay {
    position:fixed; inset:0; background:rgba(3,15,10,0.9);
    backdrop-filter:blur(12px); z-index:1000;
    display:flex; align-items:center; justify-content:center;
    padding:1rem; animation:mfade 0.2s ease;
}
.modal-overlay.hidden { display:none; }
@keyframes mfade { from{opacity:0}to{opacity:1} }
.modal-box {
    background:linear-gradient(145deg,#051409,#030d07);
    border:1px solid rgba(16,185,129,0.2); border-radius:22px;
    padding:1.4rem; width:100%; max-width:620px; max-height:88vh;
    overflow-y:auto; position:relative;
    box-shadow:0 35px 90px rgba(0,0,0,0.7);
    animation:mslide 0.28s cubic-bezier(0.175,0.885,0.32,1.275);
}
@keyframes mslide { from{transform:translateY(22px);opacity:0}to{transform:translateY(0);opacity:1} }
.modal-close {
    position:absolute; top:0.85rem; right:0.85rem;
    background:rgba(255,255,255,0.05); border:1px solid var(--border);
    color:var(--muted); width:28px; height:28px; border-radius:50%;
    display:flex; align-items:center; justify-content:center;
    cursor:pointer; transition:0.2s; font-size:0.76rem;
}
.modal-close:hover { background:var(--red); color:#fff; border-color:var(--red); }
.modal-header { display:flex; align-items:center; gap:0.9rem; margin-bottom:0.9rem; }
.modal-icon { font-size:2.2rem; }
.modal-title { font-size:1rem; font-weight:800; color:var(--text); }
.modal-sub { font-size:0.7rem; color:var(--muted); }
.learn-tabs {
    display:flex; gap:0.35rem; flex-wrap:wrap; margin-bottom:0.9rem;
    border-bottom:1px solid var(--border); padding-bottom:0.6rem;
}
.learn-tab {
    background:transparent; border:1px solid var(--border); color:var(--muted);
    padding:0.22rem 0.65rem; border-radius:7px; font-size:0.72rem; font-weight:700;
    cursor:pointer; transition:0.18s; font-family:inherit;
}
.learn-tab:hover { color:var(--green); border-color:var(--green); }
.learn-tab.active { background:var(--green); border-color:var(--green); color:#030f0a; }
.learn-section { display:none; } .learn-section.active { display:block; }
.learn-highlight {
    background:rgba(16,185,129,0.07); border-left:3px solid var(--green);
    border-radius:7px; padding:0.75rem 0.9rem; font-size:0.8rem;
    color:#86efac; font-style:italic; line-height:1.6; margin-bottom:0.9rem;
}
.learn-steps { display:flex; flex-direction:column; gap:0.55rem; }
.learn-step { display:flex; gap:0.65rem; font-size:0.78rem; color:#94a3b8; line-height:1.6; }
.learn-step strong { color:var(--text); }
.ls-num {
    background:rgba(16,185,129,0.12); color:var(--green); border-radius:50%;
    width:26px; height:26px; min-width:26px;
    display:flex; align-items:center; justify-content:center; font-size:0.64rem; font-weight:800;
}

/* ── RESPONSIVE ─────────────────────────────────────────── */
/* NOTE: Responsive layout is handled by the PhET Stage Scaling Engine
   (CSS transform: scale). Media queries are intentionally removed to
   prevent layout reflow at the real viewport width on phone screens.
   The stage is always rendered at 1280×820 and scaled down uniformly. */