/* ============================================================
   PASTEL LAB — shared base styles for the RL course
   Used by lecture-2.html through lecture-8.html (skeletons + later
   deepenings). lecture-1.html keeps its own inline styles.
   ============================================================ */

:root{
  /* palette */
  --bg:#fef8f0;
  --paper:#ffffff;
  --ink:#1f1d2b;
  --dim:#6c6a7a;
  --mint:#bff0d0;
  --peach:#ffd6c2;
  --lilac:#d8c8ff;
  --sun:#ffe27a;
  --rose:#ffb4b4;
  --sky:#bfe4ff;
  --line:#1f1d2b;
  --good:#22aa55;
  --bad:#e23e3e;

  /* typography (clamp = responsive scaling) */
  --font-display:'Cabinet Grotesk',sans-serif;
  --font-body:'General Sans',sans-serif;
  --font-mono:'JetBrains Mono',monospace;
  --title-size:clamp(2rem,6vw,5.5rem);
  --h2-size:clamp(1.6rem,4vw,3.2rem);
  --h3-size:clamp(1.1rem,2vw,1.6rem);
  --body-size:clamp(.9rem,1.3vw,1.15rem);
  --small-size:clamp(.7rem,1vw,.85rem);
  --tiny-size:clamp(.65rem,.85vw,.78rem);

  --slide-padding:clamp(1.25rem,4vw,4rem);
  --content-gap:clamp(.75rem,2vw,1.75rem);
  --element-gap:clamp(.4rem,1vw,.85rem);

  --ease:cubic-bezier(.16,1,.3,1);
}

*{margin:0;padding:0;box-sizing:border-box}
html,body{height:100%;overflow-x:hidden}
html{scroll-snap-type:y mandatory;scroll-behavior:smooth}
body{
  font-family:var(--font-body);
  background:var(--bg);
  color:var(--ink);
  font-size:var(--body-size);
  line-height:1.5;
}

/* ---- slide: viewport-locked container ---- */
.slide{
  width:100vw;
  height:100vh;
  height:100dvh;
  padding:var(--slide-padding);
  scroll-snap-align:start;
  display:flex;
  flex-direction:column;
  position:relative;
  overflow:hidden;
}
.slide-inner{
  flex:1;
  display:flex;
  flex-direction:column;
  justify-content:center;
  max-height:100%;
  overflow:hidden;
  position:relative;
  z-index:2;
}
.slide-inner.center-all{align-items:center;text-align:center}

/* ---- decorative shapes ---- */
.shape{position:absolute;pointer-events:none;z-index:1}
.shape.s-mint{background:var(--mint)}
.shape.s-peach{background:var(--peach)}
.shape.s-lilac{background:var(--lilac)}
.shape.s-sun{background:var(--sun)}
.shape.s-rose{background:var(--rose)}
.shape.s-sky{background:var(--sky)}
.shape.bordered{border:2.5px solid var(--line)}
.shape.blob{border-radius:48% 52% 60% 40%/40% 60% 38% 62%}
.shape.circle{border-radius:50%}
.shape.pill{border-radius:999px}
.shape.square{border-radius:8px}

@keyframes wobble{
  0%,100%{transform:translate(0,0) rotate(0deg)}
  50%{transform:translate(8px,-12px) rotate(6deg)}
}
@keyframes wobble-r{
  0%,100%{transform:translate(0,0) rotate(0deg)}
  50%{transform:translate(-10px,10px) rotate(-8deg)}
}
@keyframes spin{to{transform:rotate(360deg)}}
@keyframes float{
  0%,100%{transform:translateY(0)}
  50%{transform:translateY(-12px)}
}

.anim-wobble{animation:wobble 9s ease-in-out infinite}
.anim-wobble-r{animation:wobble-r 11s ease-in-out infinite}
.anim-spin-slow{animation:spin 30s linear infinite}
.anim-float{animation:float 4s ease-in-out infinite}

/* ---- typography ---- */
h1.title{
  font-family:var(--font-display);
  font-weight:800;
  font-size:var(--title-size);
  line-height:.95;
  letter-spacing:-.03em;
  margin-bottom:var(--content-gap);
}
h2.h2{
  font-family:var(--font-display);
  font-weight:700;
  font-size:var(--h2-size);
  line-height:1;
  letter-spacing:-.02em;
  margin-bottom:var(--content-gap);
}
h3.h3{
  font-family:var(--font-display);
  font-weight:600;
  font-size:var(--h3-size);
  line-height:1.1;
  letter-spacing:-.01em;
  margin-bottom:.5rem;
}
p.body{
  font-size:var(--body-size);
  color:var(--ink);
  max-width:62ch;
  line-height:1.55;
}
p.dim{color:var(--dim)}

/* ---- highlight (sun/peach/etc strike behind text) ---- */
.hl{position:relative;display:inline-block;white-space:nowrap}
.hl::after{
  content:'';position:absolute;
  left:-3px;right:-3px;bottom:6%;height:38%;
  background:var(--sun);
  z-index:-1;
  transform:skewX(-6deg);
}
.hl.mint::after{background:var(--mint)}
.hl.peach::after{background:var(--peach)}
.hl.lilac::after{background:var(--lilac)}
.hl.rose::after{background:var(--rose)}
.hl.sky::after{background:var(--sky)}

/* ---- tag pill ---- */
.tag{
  display:inline-flex;align-items:center;gap:.5rem;
  background:var(--peach);
  border:2px solid var(--line);
  padding:.4rem 1rem;border-radius:99px;
  font-family:var(--font-mono);
  font-size:var(--small-size);
  font-weight:500;
  align-self:flex-start;
  box-shadow:3px 3px 0 var(--line);
  margin-bottom:1rem;
}
.tag.mint{background:var(--mint)}
.tag.lilac{background:var(--lilac)}
.tag.sun{background:var(--sun)}
.tag.sky{background:var(--sky)}
.tag.rose{background:var(--rose)}
.tag::before{
  content:'';width:8px;height:8px;border-radius:50%;background:var(--good);
}

/* ---- card ---- */
.card{
  background:var(--paper);
  border:2.5px solid var(--line);
  border-radius:14px;
  padding:1rem 1.2rem;
  box-shadow:4px 4px 0 var(--line);
  position:relative;
}
.card.tinted-mint{background:var(--mint)}
.card.tinted-peach{background:var(--peach)}
.card.tinted-lilac{background:var(--lilac)}
.card.tinted-sun{background:var(--sun)}
.card.tinted-sky{background:var(--sky)}
.card.tinted-rose{background:var(--rose)}

/* ---- agenda steps ---- */
.steps{
  display:grid;
  grid-template-columns:repeat(5,1fr);
  gap:clamp(.5rem,1.2vw,1rem);
  margin-top:1rem;
}
.step{
  background:var(--paper);
  border:2.5px solid var(--line);
  border-radius:14px;
  padding:.9rem;
  box-shadow:4px 4px 0 var(--line);
  display:flex;flex-direction:column;
  min-height:0;
}
.step .num{
  font-family:var(--font-mono);
  font-size:var(--tiny-size);
  color:var(--dim);
  letter-spacing:.2em;
  margin-bottom:.4rem;
}
.step .ico{font-size:clamp(1.5rem,2.5vw,2rem);margin-bottom:.4rem}
.step .ttl{
  font-family:var(--font-display);
  font-weight:700;
  font-size:clamp(.9rem,1.3vw,1.1rem);
  line-height:1.1;
  margin-bottom:.3rem;
}
.step .desc{
  font-size:clamp(.7rem,.95vw,.85rem);
  color:var(--dim);
  line-height:1.4;
}
.step:nth-child(1){background:var(--mint)}
.step:nth-child(2){background:var(--peach)}
.step:nth-child(3){background:var(--lilac)}
.step:nth-child(4){background:var(--sun)}
.step:nth-child(5){background:var(--rose)}
.step:nth-child(6){background:var(--sky)}
@media (max-width:900px){
  .steps{grid-template-columns:repeat(2,1fr)}
}
.steps.cols-4{grid-template-columns:repeat(4,1fr)}
.steps.cols-6{grid-template-columns:repeat(6,1fr)}
@media (max-width:900px){
  .steps.cols-4,.steps.cols-6{grid-template-columns:repeat(2,1fr)}
}

/* ---- formula box (for tease slide) ---- */
.formula-box{
  background:var(--paper);
  border:2.5px solid var(--line);
  border-radius:18px;
  box-shadow:6px 6px 0 var(--line);
  padding:clamp(1.5rem,3vw,2.5rem) clamp(2rem,4vw,3.5rem);
  text-align:center;
  margin:1rem auto;
  max-width:800px;
}
.formula{
  font-family:'Cabinet Grotesk',serif;
  font-style:italic;
  font-weight:600;
  font-size:clamp(1.5rem,4vw,3rem);
  line-height:1.2;
  letter-spacing:-.01em;
}
.formula sub,.formula sup{
  font-size:.55em;font-style:normal;font-weight:500;
}

/* MathJax responsive sizing — display equations shrink to fit container */
.formula mjx-container[jax="SVG"]{max-width:100%}
.formula mjx-container[jax="SVG"] svg{max-width:100%;height:auto}
.formula-box mjx-container[jax="SVG"]{max-width:100%}
.formula-box mjx-container[jax="SVG"] svg{max-width:100%;height:auto}

/* ---- slide-num + slide-name footer ---- */
.slide-num{
  position:absolute;
  bottom:1rem;right:1.25rem;
  font-family:var(--font-mono);
  font-size:var(--tiny-size);
  color:var(--dim);
  letter-spacing:.18em;
  z-index:10;
}
.slide-name{
  position:absolute;
  bottom:1rem;left:1.25rem;
  font-family:var(--font-mono);
  font-size:var(--tiny-size);
  color:var(--dim);
  letter-spacing:.18em;
  text-transform:uppercase;
  z-index:10;
}

/* ---- reveal animation ---- */
.reveal{
  opacity:0;
  transform:translateY(28px);
  transition:opacity .7s var(--ease), transform .7s var(--ease);
}
.slide.visible .reveal{opacity:1;transform:translateY(0)}
.slide.visible .reveal:nth-child(1){transition-delay:.05s}
.slide.visible .reveal:nth-child(2){transition-delay:.15s}
.slide.visible .reveal:nth-child(3){transition-delay:.25s}
.slide.visible .reveal:nth-child(4){transition-delay:.35s}
.slide.visible .reveal:nth-child(5){transition-delay:.45s}
.slide.visible .reveal:nth-child(6){transition-delay:.55s}

.reveal.scale{transform:translateY(0) scale(.94)}
.slide.visible .reveal.scale{transform:translateY(0) scale(1)}

/* ---- progress bar ---- */
.progress{
  position:fixed;top:0;left:0;height:4px;
  background:var(--ink);
  z-index:1000;
  transition:width .25s var(--ease);
  width:0;
}

/* ---- nav dots ---- */
.nav{
  position:fixed;right:18px;top:50%;
  transform:translateY(-50%);
  display:flex;flex-direction:column;gap:8px;
  z-index:100;
}
.nav button{
  width:10px;height:10px;border-radius:50%;
  border:1.5px solid var(--line);
  background:transparent;cursor:pointer;
  padding:0;transition:all .3s var(--ease);
}
.nav button.active{background:var(--ink);transform:scale(1.4)}
.nav button:hover{background:var(--sun)}

/* ---- keyboard hint ---- */
.hint{
  position:fixed;bottom:8px;left:50%;
  transform:translateX(-50%);
  font-family:var(--font-mono);
  font-size:var(--tiny-size);
  color:var(--dim);
  letter-spacing:.18em;
  pointer-events:none;
  z-index:100;
  background:var(--bg);
  padding:.25rem .75rem;
  border-radius:99px;
  border:1px solid rgba(31,29,43,0.1);
}

/* ---- "under construction" placeholder for skeleton ---- */
.placeholder{
  background:var(--paper);
  border:2.5px dashed var(--line);
  border-radius:18px;
  box-shadow:5px 5px 0 var(--line);
  padding:clamp(1.5rem,3vw,2.5rem);
  text-align:center;
  max-width:760px;
  margin:0 auto;
}
.placeholder .badge{
  display:inline-block;
  font-family:var(--font-mono);
  font-size:var(--small-size);
  letter-spacing:.2em;
  background:var(--sun);
  border:2px solid var(--line);
  padding:.3rem .9rem;
  border-radius:99px;
  box-shadow:2px 2px 0 var(--line);
  margin-bottom:1rem;
}
.placeholder p{
  font-size:clamp(.95rem,1.3vw,1.1rem);
  color:var(--ink);
  line-height:1.6;
  margin-bottom:.8rem;
}

/* ---- prev/next links ---- */
.lecture-nav{
  display:flex;justify-content:space-between;
  gap:1rem;flex-wrap:wrap;
  margin-top:1.2rem;
}
.lecture-nav a{
  display:inline-flex;align-items:center;gap:.5rem;
  background:var(--paper);
  border:2.5px solid var(--line);
  border-radius:99px;
  padding:.55rem 1.2rem;
  text-decoration:none;
  color:var(--ink);
  font-family:var(--font-mono);
  font-weight:600;
  font-size:var(--small-size);
  box-shadow:3px 3px 0 var(--line);
  transition:transform .15s var(--ease),box-shadow .15s var(--ease);
}
.lecture-nav a:hover{
  transform:translate(-2px,-2px);
  box-shadow:5px 5px 0 var(--line);
}
.lecture-nav a.next{background:var(--mint)}
.lecture-nav a.prev{background:var(--peach)}
.lecture-nav a.home{background:var(--lilac)}

/* ---- responsive ---- */
@media (max-height:700px){
  :root{
    --slide-padding:clamp(.75rem,3vw,2rem);
    --content-gap:clamp(.4rem,1.5vw,1rem);
    --title-size:clamp(1.5rem,4.5vw,3rem);
    --h2-size:clamp(1.2rem,3vw,2rem);
  }
}
@media (max-height:600px){
  :root{
    --slide-padding:clamp(.5rem,2.5vw,1.5rem);
    --title-size:clamp(1.25rem,4vw,2.5rem);
    --body-size:clamp(.75rem,1.1vw,.9rem);
  }
  .nav{display:none}
  .hint{display:none}
}
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{
    animation-duration:.01ms!important;
    transition-duration:.2s!important;
  }
  html{scroll-behavior:auto}
}