/* ── Slide system ── */
.slide-container {
    position: absolute;
    inset: 0 0 var(--deck-nav-height) 0;
    overflow: hidden;
  }
  .slide {
    position: absolute;
    inset: 0;
    display: none;
    flex-direction: column;
    padding: 1.2rem 2.35rem 1rem;
    overflow: hidden;
    animation: fadeSlideIn 0.4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  }
  .slide.active { display: flex; }

  @keyframes fadeSlideIn {
    from { opacity: 0; transform: translateY(1rem); }
    to   { opacity: 1; transform: translateY(0); }
  }

  .slide.centered {
    align-items: center;
    justify-content: center;
    text-align: center;
  }

/* ── Cards ── */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 0.875rem;
    padding: var(--sp-4);
    position: relative;
    overflow: visible;
  }
  .card::before {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: inherit;
    background: radial-gradient(ellipse at top left, rgba(26,69,200,0.04), transparent 60%);
    pointer-events: none;
  }

/* ── Callouts ── */
.callout {
    display: flex;
    gap: var(--sp-2);
    padding: var(--sp-3) var(--sp-4);
    border-radius: var(--radius-md);
    font-size: var(--fs-sm);
    line-height: 1.55;
  }
  .callout.info    { background: var(--accent-bg);  border: 1px solid var(--accent-border); color: #112580; }
  .callout.warn    { background: var(--orange-bg);   border: 1px solid var(--orange-border);  color: #6a2e00; }
  .callout.success { background: var(--green-bg);   border: 1px solid var(--green-border);  color: #0a4a20; }
  .callout.question { background: var(--purple-bg); border: 1px solid var(--purple-border); color: #340e8a; }
  .callout.pink    { background: rgba(170,24,104,0.07);  border: 1px solid rgba(170,24,104,0.30); color: #700040; }
  .callout .icon { flex-shrink: 0; font-size: var(--fs-lg); }
  .editor-note {
    margin-top: var(--sp-3);
    max-width: 52rem;
    background: var(--red-bg);
    border: 1px solid var(--red-border);
    color: #780000;
    border-radius: var(--radius-md);
    padding: var(--sp-3) var(--sp-4);
    font-size: var(--fs-xs);
    line-height: 1.55;
    text-align: left;
  }
  .editor-note strong {
    color: var(--red);
    letter-spacing: 0.04em;
  }

/* ── Badges / pills ── */
.badge {
    display: inline-block;
    position: absolute;
    top: 0.48rem;
    left: 0.68rem;
    z-index: 2;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 0.22rem 0.62rem;
    border-radius: var(--radius-full);
    margin-bottom: 0;
  }
  .badge.day1 { background: rgba(26,69,200,0.12); color: var(--accent); }
  .badge.activity { background: rgba(21,116,60,0.12); color: var(--green); }
  .badge.concept { background: rgba(88,40,184,0.12); color: var(--purple); }
  .badge.discussion { background: rgba(158,74,0,0.12); color: var(--orange); }
  .badge.deepdive { background: rgba(140,108,0,0.12); color: var(--yellow); }

/* ── Grid layouts ── */
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: var(--sp-4); }
  .grid-3 { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: var(--sp-4); }
  .grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--sp-4); }

/* ── Flow diagrams ── */
.flow {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--sp-2);
    flex-wrap: wrap;
    margin: var(--sp-3) 0;
  }
  .flow-box {
    padding: var(--sp-3) var(--sp-4);
    border-radius: var(--radius-md);
    font-size: var(--fs-sm);
    font-weight: 600;
    text-align: center;
    border: 1px solid var(--border);
    background: var(--surface);
    min-width: 6.25rem;
  }
  .flow-arrow {
    display: none;
  }
  .flow .flow-box ~ .flow-box {
    position: relative;
    margin-left: 1.5rem;
  }
  .flow .flow-box ~ .flow-box::before {
    content: '→';
    position: absolute;
    right: calc(100% + 0.25rem);
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-dim);
    font-size: var(--fs-lg);
    pointer-events: none;
  }
  .flow-loop {
    color: var(--text-dim);
    font-size: var(--fs-lg);
    flex-shrink: 0;
  }
  .flow-box.data    { border-color: rgba(0,104,128,0.55); color: var(--cyan); background: rgba(0,104,128,0.07); }
  .flow-box.model   { border-color: rgba(26,69,200,0.55); color: var(--accent); background: rgba(26,69,200,0.07); }
  .flow-box.blue    { border-color: rgba(26,69,200,0.55); color: var(--accent); background: rgba(26,69,200,0.07); }
  .flow-box.loss    { border-color: rgba(184,24,24,0.55); color: var(--red); background: rgba(184,24,24,0.07); }
  .flow-box.grad    { border-color: rgba(158,74,0,0.55); color: var(--orange); background: rgba(158,74,0,0.07); }
  .flow-box.param   { border-color: rgba(88,40,184,0.55); color: var(--purple); background: rgba(88,40,184,0.07); }
  .flow-box.target  { border-color: rgba(21,116,60,0.65); color: var(--green); background: rgba(21,116,60,0.08); border-style: dashed; }
  .flow-box.green   { border-color: rgba(21,116,60,0.55); color: var(--green); background: rgba(21,116,60,0.07); }
  .flow-box.pink    { border-color: rgba(170,24,104,0.55); color: var(--pink); background: rgba(170,24,104,0.07); }
  .flow-box.yellow  { border-color: rgba(140,108,0,0.55); color: var(--yellow); background: rgba(140,108,0,0.07); }

/* Backward flow — arrows point left for backpropagation */
.flow.flow-backward .flow-box ~ .flow-box::before { content: '←'; }

/* ── Bottom nav ── */
.bottom-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: absolute;
    left: 0;
    right: 0;
    bottom: 0;
    height: var(--deck-nav-height);
    padding: 0 0.85rem;
    box-sizing: border-box;
    background: rgba(255,255,255,0.96);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid var(--border);
    z-index: 10;
    flex-shrink: 0;
  }
  .progress-track {
    flex: 1;
    height: 0.16rem;
    background: var(--surface2);
    border-radius: 0.2rem;
    margin: 0 0.85rem;
    overflow: hidden;
  }
  .progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--purple));
    border-radius: 0.2rem;
    transition: width 0.4s ease;
  }
  .nav-btn {
    font-family: 'Inter', sans-serif;
    font-size: 0.72rem;
    font-weight: 600;
    padding: 0.19rem 0.70rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--surface2);
    color: var(--text);
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
  }
  .nav-btn:hover { background: var(--border); }
  .nav-btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
  .nav-btn.primary:hover { background: #1238a8; }
  .nav-btn:disabled { opacity: 0.3; cursor: not-allowed; }
  .slide-counter {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.68rem;
    color: var(--text-dim);
    min-width: 3.1rem;
    text-align: center;
  }

/* ── Objective list ── */
.obj-list { list-style: none; margin: var(--sp-2) 0; }
  .obj-list li {
    padding: var(--sp-2) var(--sp-3) var(--sp-2) 2.25rem;
    border-radius: var(--radius-sm);
    margin-bottom: var(--sp-2);
    font-size: var(--fs-sm);
    line-height: 1.5;
    background: var(--surface2);
    border: 1px solid var(--border);
    position: relative;
  }
  .obj-list li::before {
    content: attr(data-num);
    position: absolute;
    left: var(--sp-3);
    top: var(--sp-2);
    font-family: 'JetBrains Mono', monospace;
    font-size: var(--fs-xs);
    font-weight: 700;
    color: var(--accent);
  }

  .loop-arrow-anim { animation: pulseGlow 1.5s ease-in-out infinite; }
  @keyframes pulseGlow { 0%, 100% { opacity: 0.5; } 50% { opacity: 1; } }

  .section-tag {
    position: absolute;
    top: 0.5rem;
    right: 0.7rem;
    left: auto;
    font-size: 0.66rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.07em;
    color: var(--text-dim);
    opacity: 0.42;
  }

  .slide:not(.centered) > h2,
  .slide:not(.centered) > h1,
  .slide:not(.centered) > .spacer,
  .slide:not(.centered) > .spacer-sm,
  .slide:not(.centered) > .spacer-lg,
  .slide:not(.centered) > .gradient-line,
  .slide:not(.centered) > .grid-2,
  .slide:not(.centered) > .grid-3,
  .slide:not(.centered) > .grid-4,
  .slide:not(.centered) > .card {
    margin-top: 0.60rem;
  }