/* ===== Probability Course — Design System ===== */
/* 主色：indigo → violet 表达"随机/概率分布" */
:root {
    --prob-indigo: #4f46e5;
    --prob-violet: #7c3aed;
    --prob-blue: #2563eb;
    --prob-gradient: linear-gradient(135deg, #4f46e5 0%, #7c3aed 100%);
    --radius: 14px;
    --transition: 0.25s cubic-bezier(0.25, 0.8, 0.25, 1);
}

/* ---- Keyframes ---- */
@keyframes slideUp { 0% {opacity:0;transform:translateY(20px);} 100% {opacity:1;transform:translateY(0);} }
@keyframes fadeIn  { 0% {opacity:0;} 100% {opacity:1;} }
@keyframes shimmer { 0%,100% {background-position:0% 50%;} 50% {background-position:100% 50%;} }
@keyframes floatOrb { 0%,100% {transform:translateY(0) scale(1);} 50% {transform:translateY(-30px) scale(1.05);} }
@keyframes spin { to { transform: rotate(360deg); } }

/* ---- Navigation ---- */
.nav-glass {
    background: rgba(255,255,255,0.82);
    backdrop-filter: blur(16px) saturate(1.6);
    -webkit-backdrop-filter: blur(16px) saturate(1.6);
    border-bottom: 1px solid rgba(226,232,240,0.7);
}
.nav-pill {
    padding: 6px 13px; border-radius: 9999px;
    font-size: 13px; font-weight: 500;
    color: #475569;
    transition: all var(--transition);
    white-space: nowrap;
}
.nav-pill:hover { background: rgba(241,245,249,0.8); color: #1e293b; }
.nav-pill.active { background: var(--prob-gradient); color: #fff; box-shadow: 0 1px 4px rgba(79,70,229,0.3); }

/* ---- Glass Card ---- */
.glass-card {
    background: rgba(255,255,255,0.72);
    backdrop-filter: blur(12px) saturate(1.4);
    -webkit-backdrop-filter: blur(12px) saturate(1.4);
    border: 1px solid rgba(226,232,240,0.8);
    border-radius: var(--radius);
    padding: 20px;
    transition: all var(--transition);
}
.glass-card:hover {
    border-color: rgba(79,70,229,0.2);
    box-shadow: 0 8px 24px -8px rgba(79,70,229,0.12);
}

/* ---- Buttons ---- */
.btn-primary {
    display: inline-flex; align-items: center; justify-content: center; gap: 6px;
    padding: 8px 20px; border-radius: 12px;
    background: var(--prob-gradient); color: #fff;
    font-size: 14px; font-weight: 600;
    border: none; cursor: pointer;
    transition: all var(--transition);
    box-shadow: 0 2px 8px -2px rgba(79,70,229,0.35);
}
.btn-primary:hover { box-shadow: 0 4px 16px -4px rgba(79,70,229,0.45); transform: translateY(-1px); }
.btn-secondary {
    display: inline-flex; align-items: center; justify-content: center; gap: 6px;
    padding: 8px 20px; border-radius: 12px;
    background: rgba(255,255,255,0.8);
    color: #334155; font-size: 14px; font-weight: 600;
    border: 1px solid rgba(226,232,240,0.8);
    cursor: pointer; transition: all var(--transition);
}
.btn-secondary:hover { background: #fff; border-color: rgba(79,70,229,0.3); color: #4f46e5; }

/* ---- Typography ---- */
.stat-num { font-variant-numeric: tabular-nums; letter-spacing: -0.02em; }
.gradient-shimmer {
    background: linear-gradient(135deg, #4f46e5 0%, #7c3aed 40%, #4f46e5 100%);
    background-size: 200% 200%;
    -webkit-background-clip: text; background-clip: text;
    -webkit-text-fill-color: transparent;
    animation: shimmer 4s ease-in-out infinite;
}

/* ---- Grid dots ---- */
.grid-dots {
    background-image: radial-gradient(circle, #94a3b8 0.8px, transparent 0.8px);
    background-size: 32px 32px;
}

.float-orb { animation: floatOrb 8s ease-in-out infinite; }
.float-orb-slow { animation: floatOrb 12s ease-in-out infinite reverse; }

.card-stagger { opacity: 0; animation: slideUp 0.5s cubic-bezier(0.25,0.8,0.25,1) forwards; }

/* ===== Hero cards ===== */
.hero-feature-card {
    background: rgba(255,255,255,0.7);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(226,232,240,0.8);
    border-radius: 16px;
    padding: 28px 22px;
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    position: relative; overflow: hidden;
    display: block;
}
.hero-feature-card::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
    background: var(--card-accent, var(--prob-gradient));
    opacity: 0; transition: opacity 0.3s;
}
.hero-feature-card:hover::before { opacity: 1; }
.hero-feature-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 20px 40px -12px rgba(79,70,229,0.14);
    border-color: rgba(79,70,229,0.2);
}
.hero-feature-card .card-icon-ring {
    width: 56px; height: 56px; border-radius: 16px;
    display: flex; align-items: center; justify-content: center;
    position: relative;
    transition: transform 0.3s;
}
.hero-feature-card:hover .card-icon-ring { transform: scale(1.1); }

/* ---- Module row ---- */
.module-row {
    display: flex; align-items: center; gap: 16px;
    padding: 14px 18px;
    background: rgba(255,255,255,0.6);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(226,232,240,0.6);
    border-radius: 14px;
    transition: all 0.25s cubic-bezier(0.25, 0.8, 0.25, 1);
    text-decoration: none;
}
.module-row:hover {
    background: rgba(255,255,255,0.9);
    box-shadow: 0 4px 16px -4px rgba(79,70,229,0.12);
    transform: translateX(4px);
}

/* ---- Definition blocks (chapter knowledge) ---- */
.def-block { border-left: 4px solid var(--prob-indigo); background: rgba(238, 242, 255, 0.5); padding: 14px 18px; border-radius: 10px; margin: 10px 0; }
.def-block.def { border-color: #4f46e5; background: rgba(238, 242, 255, 0.55); }
.def-block.thm { border-color: #059669; background: rgba(209, 250, 229, 0.45); }
.def-block.prop { border-color: #7c3aed; background: rgba(237, 233, 254, 0.5); }
.def-block.ex  { border-color: #f59e0b; background: rgba(254, 243, 199, 0.5); }
.def-kind-tag { display: inline-block; padding: 2px 8px; border-radius: 6px; font-size: 11px; font-weight: 700; letter-spacing: 0.05em; margin-right: 8px; }
.def-kind-tag.def { background: #4f46e5; color: white; }
.def-kind-tag.thm { background: #059669; color: white; }
.def-kind-tag.prop { background: #7c3aed; color: white; }
.def-kind-tag.ex { background: #f59e0b; color: white; }

/* ---- Lab iframe shell ---- */
.lab-frame {
    width: 100%; height: 720px; border: 0;
    border-radius: 0 0 14px 14px;
    background: white;
    display: block;
}
.lab-hero-banner {
    background: var(--card-accent, var(--prob-gradient));
    color: white;
    border-radius: 20px;
    padding: 32px 28px;
    position: relative;
    overflow: hidden;
}
.lab-hero-banner::after {
    content: ''; position: absolute; top: -20%; right: -10%;
    width: 300px; height: 300px;
    background: radial-gradient(circle, rgba(255,255,255,0.15), transparent 65%);
    pointer-events: none;
}
.lab-detail-page .glass-card {
    background: rgba(255,255,255,0.82);
}
.lab-detail-hero {
    box-shadow: 0 22px 48px -28px rgba(15,23,42,0.45);
}
.lab-detail-hero__icon {
    width: 72px;
    height: 72px;
    border-radius: 18px;
    background: rgba(255,255,255,0.16);
    border: 1px solid rgba(255,255,255,0.24);
    backdrop-filter: blur(10px);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 42px;
    flex-shrink: 0;
}
.lab-detail-hero__eyebrow {
    font-size: 12px;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    opacity: 0.78;
    margin-bottom: 5px;
}
.lab-detail-hero__tags {
    display: flex;
    flex-wrap: wrap;
    gap: 7px;
    max-width: 360px;
}
.lab-detail-hero__tags span {
    font-size: 11px;
    padding: 5px 9px;
    border-radius: 999px;
    background: rgba(255,255,255,0.15);
    border: 1px solid rgba(255,255,255,0.2);
}
.lab-panel {
    box-shadow: 0 18px 42px -34px rgba(15,23,42,0.45);
}
.lab-panel-title {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
    font-weight: 800;
    color: #1e293b;
    margin-bottom: 12px;
}
.lab-runner-card {
    overflow: hidden;
    border-radius: 16px;
    box-shadow: 0 22px 56px -36px rgba(15,23,42,0.52);
}
.lab-runner-card__bar {
    min-height: 64px;
    padding: 14px 16px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 14px;
    background: linear-gradient(180deg, rgba(255,255,255,0.96), rgba(248,250,252,0.92));
    border-bottom: 1px solid rgba(226,232,240,0.86);
}
.lab-open-link {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    font-size: 11px;
    color: #475569;
    padding: 7px 10px;
    border-radius: 999px;
    border: 1px solid rgba(203,213,225,0.9);
    background: #fff;
    transition: all var(--transition);
    white-space: nowrap;
}
.lab-open-link:hover {
    color: #4f46e5;
    border-color: rgba(99,102,241,0.36);
    box-shadow: 0 8px 22px -18px rgba(79,70,229,0.7);
}
.lab-status-pill {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 11px;
    color: #047857;
    padding: 7px 10px;
    border-radius: 999px;
    background: #ecfdf5;
    border: 1px solid rgba(16,185,129,0.22);
    white-space: nowrap;
}
.lab-status-pill span {
    width: 7px;
    height: 7px;
    border-radius: 999px;
    background: #10b981;
    box-shadow: 0 0 0 4px rgba(16,185,129,0.13);
}
.lab-info-item {
    padding: 12px;
    background: rgba(255,255,255,0.74);
    border-radius: 10px;
    border: 1px solid rgba(226,232,240,0.9);
}
.lab-observe-list {
    display: grid;
    gap: 10px;
    font-size: 12.5px;
    color: #334155;
    line-height: 1.65;
}
.lab-observe-list li {
    display: flex;
    gap: 9px;
}
.lab-observe-list li > span {
    width: 21px;
    height: 21px;
    border-radius: 999px;
    background: var(--prob-gradient);
    color: white;
    font-size: 10px;
    font-weight: 800;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    margin-top: 1px;
}
.lab-help-card {
    background: linear-gradient(135deg, rgba(238,242,255,0.88), rgba(240,253,250,0.78)) !important;
    border-color: rgba(129,140,248,0.26) !important;
}

/* ---- Flash ---- */
.flash { position: fixed; top: 5rem; left: 50%; transform: translateX(-50%); z-index: 80;
    padding: 10px 20px; border-radius: 10px; box-shadow: 0 4px 12px rgba(0,0,0,0.1); }
.flash.success { background: #dcfce7; color: #15803d; }
.flash.error { background: #fee2e2; color: #b91c1c; }

/* ---- Responsive ---- */
@media (max-width: 1023px) {
    .nav-pill { padding: 5px 10px; font-size: 12px; }
    .hero-feature-card { padding: 20px 16px; }
    .lab-frame { height: 760px; }
    .lab-runner-card__bar { align-items: flex-start; flex-direction: column; }
}
@supports (padding-bottom: env(safe-area-inset-bottom)) {
    body { padding-bottom: env(safe-area-inset-bottom); }
}