/* =========================================================
   CS210 · Lecture 4 Interactive Demos — shared stylesheet
   Lifecycle and ViewGroup
   ---------------------------------------------------------
   Same design language as week01.css: same tokens, same nav,
   same two-column section layout.  Kept inside week04/ so the
   folder can be copied to a lecture machine on its own.
   ========================================================= */
:root{
  --ink:#1d1d1f;
  --ink-2:#6e6e73;
  --ink-3:#86868b;
  --line:#d2d2d7;
  --line-soft:#e8e8ed;
  --bg:#ffffff;
  --bg-2:#f5f5f7;
  --bg-3:#ececed;
  --accent:#0066cc;
  --accent-soft:#e9f1fb;
  --warn:#b25000;
  --warn-soft:#fff3e3;
  --danger:#c8102e;
  --danger-soft:#fdecef;
  --ok:#0f7b3f;
  --ok-soft:#e9f5ee;
  --radius:14px;
  --mono:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Consolas,"Liberation Mono",monospace;
}
*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:var(--bg);
  color:var(--ink);
  font-family:-apple-system,BlinkMacSystemFont,"SF Pro Display","Segoe UI","Helvetica Neue","PingFang SC","Microsoft YaHei",sans-serif;
  font-size:17px;
  line-height:1.55;
  -webkit-font-smoothing:antialiased;
}
.wrap{max-width:1120px;margin:0 auto;padding:0 40px;}

/* ---------- top bar ---------- */
.nav{
  position:sticky;top:0;z-index:50;
  background:rgba(255,255,255,.86);
  backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid var(--line-soft);
}
.nav-inner{max-width:1120px;margin:0 auto;padding:0 40px;height:54px;display:flex;align-items:center;gap:22px;}
.nav .brand{font-size:13px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-2);font-weight:600;text-decoration:none;}
.nav .brand:hover{color:var(--ink);}
.nav .here{font-size:13.5px;color:var(--ink-3);}
.nav .spacer{margin-left:auto;}
.nav a.jump{font-size:14px;color:var(--ink-2);text-decoration:none;}
.nav a.jump:hover{color:var(--ink);}

/* ---------- page head ---------- */
.page-head{padding:60px 0 44px;border-bottom:1px solid var(--line-soft);}
.page-head .num{font-family:var(--mono);font-size:12.5px;color:var(--accent);letter-spacing:.1em;}
.page-head h1{font-size:clamp(32px,4.4vw,52px);line-height:1.07;letter-spacing:-.025em;font-weight:680;margin:12px 0 16px;}
.page-head p.lede{font-size:20px;color:var(--ink-2);max-width:64ch;margin:0;}

/* ---------- sections ---------- */
section{border-bottom:1px solid var(--line-soft);}
section:nth-of-type(even){background:var(--bg-2);}
.sec{padding:80px 0;}
.grid{display:grid;grid-template-columns:250px 1fr;gap:60px;align-items:start;}
.side{position:sticky;top:96px;}
.side h2{font-size:22px;line-height:1.2;letter-spacing:-.015em;margin:0 0 10px;font-weight:660;}
.side .why{font-size:14.5px;color:var(--ink-2);margin:0;}
.side .ask{margin-top:20px;padding-top:16px;border-top:1px solid var(--line);font-size:14.5px;}
.side .ask span{display:block;font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);margin-bottom:6px;}
.side .mini{margin-top:16px;font-size:13.5px;color:var(--ink-3);}
h3.sub{font-size:12px;letter-spacing:.12em;text-transform:uppercase;color:var(--ink-3);margin:0 0 14px;font-weight:600;}

/* ---------- controls ---------- */
.btn{
  font:inherit;font-size:15px;padding:9px 18px;border-radius:980px;border:1px solid var(--line);
  background:#fff;color:var(--ink);cursor:pointer;transition:.16s;
}
.btn:hover{border-color:var(--ink-3);}
.btn.primary{background:var(--accent);border-color:var(--accent);color:#fff;}
.btn.primary:hover{background:#0058b0;}
.btn.small{font-size:13.5px;padding:6px 14px;}
.btn[aria-pressed="true"]{background:var(--ink);border-color:var(--ink);color:#fff;}
.btn:disabled{opacity:.42;cursor:not-allowed;}
.btn.on-good[aria-pressed="true"]{background:var(--ok);border-color:var(--ok);color:#fff;}
.btn.on-bad[aria-pressed="true"]{background:var(--danger);border-color:var(--danger);color:#fff;}

.reveal{margin-top:20px;border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:22px 24px;display:none;}
.reveal.show{display:block;animation:fade .28s ease;}
@keyframes fade{from{opacity:0;transform:translateY(6px);}to{opacity:1;transform:none;}}

.pill{display:inline-block;border:1px solid var(--line);border-radius:980px;padding:5px 14px;font-size:14px;background:#fff;margin:0 8px 8px 0;}
.pill.key{border-color:var(--accent);background:var(--accent-soft);color:#004b96;font-weight:600;}

/* ---------- code ---------- */
.codebox{border:1px solid var(--line);border-radius:12px;background:#fff;overflow:hidden;}
.codebox .file{font-family:var(--mono);font-size:12px;color:var(--ink-2);padding:9px 16px;border-bottom:1px solid var(--line-soft);background:var(--bg-2);}
.codebox pre{margin:0;padding:18px 20px;font-family:var(--mono);font-size:13.5px;line-height:1.65;overflow-x:auto;color:#1d1d1f;}
.codebox .k{color:#7a1f7a;}
.codebox .s{color:#0a6b2c;}
.codebox .c{color:var(--ink-3);}
.codebox .a{color:#9a3b00;}
.codebox .hl{background:#fff3c4;border-radius:3px;padding:0 2px;}

/* ---------- photographs ---------- */
.photo{position:relative;overflow:hidden;border-radius:var(--radius);background:var(--bg-3);border:1px solid var(--line-soft);}
.photo > img{display:block;width:100%;height:100%;object-fit:cover;object-position:center;}
.photo.lift{box-shadow:0 6px 22px rgba(0,0,0,.07);}
.credit{margin-top:9px;font-size:11.5px;line-height:1.5;color:var(--ink-3);}
.credit b{color:var(--ink-2);font-weight:600;}
.credit a{color:var(--ink-3);text-decoration:none;border-bottom:1px solid var(--line);}
.credit a:hover{color:var(--ink-2);border-bottom-color:var(--ink-3);}
.fig-row{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:20px;}
.fig-photo{height:190px;}

/* ---------- the phone shell (shared by demos 1, 2, 4) ---------- */
.stage{
  background:var(--bg-3);border-radius:20px;padding:40px 24px;
  display:flex;justify-content:center;align-items:flex-start;gap:28px;flex-wrap:wrap;
}
.dev{
  width:300px;flex:0 0 auto;background:#fff;border:1px solid #d8d8dd;border-radius:32px;
  box-shadow:0 20px 50px rgba(0,0,0,.13);overflow:hidden;display:flex;flex-direction:column;
  transition:width .25s ease;
}
.dev.landscape{width:380px;}
.dev-bar{
  height:28px;display:flex;align-items:center;justify-content:space-between;padding:0 14px;
  font-size:11px;font-family:var(--mono);color:var(--ink-3);border-bottom:1px solid var(--line-soft);background:#fbfbfd;
}
.dev-body{flex:1 1 auto;background:#fff;position:relative;min-height:340px;}
.dev-foot{height:34px;border-top:1px solid var(--line-soft);background:#fbfbfd;display:flex;align-items:center;justify-content:space-around;font-size:15px;color:var(--ink-3);}
.dev-foot .sysbtn{cursor:pointer;padding:0 12px;border-radius:8px;transition:.14s;user-select:none;}
.dev-foot .sysbtn:hover{background:var(--bg-3);color:var(--ink);}

/* ---------- Demo 01 · lifecycle ---------- */
.appscreen{padding:20px 18px;min-height:330px;display:flex;flex-direction:column;}
.appscreen .apptitle{font-size:13px;color:var(--ink-3);text-align:center;margin-bottom:14px;letter-spacing:.04em;}
.clockface{
  font-family:var(--mono);font-size:44px;font-weight:600;letter-spacing:-.02em;
  text-align:center;font-variant-numeric:tabular-nums;margin:14px 0 4px;
}
.clockface.dim{opacity:.28;}
.appscreen .buttons{display:flex;gap:8px;justify-content:center;margin-top:20px;flex-wrap:wrap;}
.appscreen .buttons .btn{font-size:13px;padding:7px 16px;}
.screen-empty{
  position:absolute;inset:0;display:flex;align-items:center;justify-content:center;
  background:#fbfbfd;color:var(--ink-3);font-size:14px;text-align:center;padding:30px;line-height:1.5;
}
.screen-cover{
  position:absolute;inset:0;background:rgba(20,20,22,.72);color:#fff;
  display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:26px;gap:8px;
}
.screen-cover .q{font-size:20px;font-weight:640;letter-spacing:-.02em;line-height:1.25;}
.screen-cover .s{font-size:13px;color:rgba(255,255,255,.72);}
.screen-cover .btn{background:transparent;border-color:rgba(255,255,255,.55);color:#fff;font-size:13px;padding:6px 14px;}
.screen-cover .btn:hover{border-color:#fff;}

.life-cols{display:grid;grid-template-columns:1fr 1fr;gap:26px;align-items:start;}
.ladder{border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:16px 18px;}
.ladder h4{margin:0 0 12px;font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);font-weight:600;}
.rung{
  display:flex;align-items:center;gap:10px;padding:7px 10px;border-radius:8px;font-size:14px;
  color:var(--ink-3);transition:.2s;
}
.rung .dot{width:8px;height:8px;border-radius:50%;background:var(--line);flex:0 0 8px;transition:.2s;}
.rung .m{font-family:var(--mono);font-size:13px;}
.rung.on{background:var(--accent-soft);color:#004b96;font-weight:620;}
.rung.on .dot{background:var(--accent);transform:scale(1.35);}
.rung.dead{color:var(--line);}
.rung.dead .m{text-decoration:line-through;}

.logbox{border:1px solid var(--line);border-radius:var(--radius);background:#fff;overflow:hidden;display:flex;flex-direction:column;}
.logbox .head{
  display:flex;align-items:center;justify-content:space-between;padding:10px 16px;border-bottom:1px solid var(--line-soft);
  background:var(--bg-2);font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);font-weight:600;
}
.logbox .head button{font:inherit;font-size:11.5px;letter-spacing:.06em;border:0;background:none;color:var(--accent);cursor:pointer;text-transform:uppercase;}
.log{list-style:none;margin:0;padding:10px 0;min-height:262px;max-height:262px;overflow-y:auto;font-family:var(--mono);font-size:12.5px;}
.log li{display:flex;gap:10px;padding:5px 16px;animation:slide .22s ease;}
@keyframes slide{from{opacity:0;transform:translateX(-6px);}to{opacity:1;transform:none;}}
.log .n{color:var(--ink-3);flex:0 0 24px;text-align:right;}
.log .m{font-weight:600;}
.log .a{color:var(--ink-3);}
.log li.enter .m{color:var(--accent);}
.log li.exit .m{color:var(--warn);}
.log li.dead .m{color:var(--danger);}
.log li.born .m{color:var(--ok);}
.log li .why{margin-left:auto;color:var(--ink-3);font-size:11.5px;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;}
.log li.note{padding-top:2px;padding-bottom:6px;}
.log li.note .m{color:var(--ink-3);font-weight:400;font-style:italic;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;}
.log .empty{padding:16px;color:var(--ink-3);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;font-size:13.5px;}

/* live flags strip */
.status-strip{
  margin-top:24px;border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:15px 20px;
  font-size:14.5px;color:var(--ink-2);display:flex;flex-wrap:wrap;gap:8px 26px;
}
.status-strip b{color:var(--ink);font-weight:600;}
.status-strip .bad{color:var(--danger);font-weight:600;}
.status-strip .good{color:var(--ok);font-weight:600;}

.ctl-grid{margin-top:26px;display:grid;grid-template-columns:repeat(auto-fit,minmax(190px,1fr));gap:18px 22px;}
.ctl .lab{font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);margin-bottom:9px;}
.ctl .row{display:flex;gap:8px;flex-wrap:wrap;}

.verdict{
  margin-top:22px;border:1px solid var(--line);border-left-width:3px;border-radius:0 12px 12px 0;
  padding:14px 20px;font-size:15px;background:#fff;transition:.2s;
}
.verdict .tag{display:block;font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;margin-bottom:3px;color:var(--ink-3);}
.verdict.bad{border-left-color:var(--danger);background:var(--danger-soft);}
.verdict.bad .tag{color:var(--danger);}
.verdict.good{border-left-color:var(--ok);background:var(--ok-soft);}
.verdict.good .tag{color:var(--ok);}

/* ---------- Demo 02 · state ---------- */
.bundle{border:1px solid var(--line);border-radius:var(--radius);background:#fff;overflow:hidden;}
.bundle .head{padding:10px 16px;border-bottom:1px solid var(--line-soft);background:var(--bg-2);font-size:11.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);font-weight:600;}
.bundle table{width:100%;border-collapse:collapse;font-family:var(--mono);font-size:12.5px;}
.bundle th{text-align:left;font-weight:600;color:var(--ink-3);font-size:11px;letter-spacing:.06em;padding:9px 16px 6px;border-bottom:1px solid var(--line-soft);}
.bundle td{padding:7px 16px;border-bottom:1px solid var(--line-soft);}
.bundle tr:last-child td{border-bottom:0;}
.bundle .empty{padding:18px 16px;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;font-size:13.5px;color:var(--ink-3);}
.bundle td.k{color:#7a1f7a;}
.bundle td.v{color:#0a6b2c;}

/* ---------- Demo 03 · view hierarchy ---------- */
.vtree{border:1px solid var(--line);border-radius:12px;background:#fff;padding:14px 10px;font-family:var(--mono);font-size:12.5px;line-height:1.5;}
.tnode{
  display:flex;align-items:center;gap:9px;padding:6px 10px;border-radius:7px;cursor:pointer;
  transition:.14s;border:1px solid transparent;
}
.tnode:hover{background:var(--bg-2);}
.tnode.on{background:var(--accent-soft);border-color:var(--accent);}
.tnode .ind{color:var(--line);}
.tnode .tag{color:var(--ink);}
.tnode.is-group .tag{font-weight:700;}
.tnode .cnt{margin-left:auto;font-size:11px;color:var(--ink-3);}
.tnode.on .cnt{color:#004b96;}
.inspector{border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:24px 26px;min-height:332px;}
.inspector h4{margin:0 0 4px;font-size:20px;letter-spacing:-.015em;font-family:var(--mono);}
.inspector .kind{font-family:var(--mono);font-size:12px;color:var(--ink-3);margin-bottom:16px;}
.inspector p.desc{margin:0 0 16px;font-size:15px;color:var(--ink-2);}
.inspector .kv{display:grid;grid-template-columns:110px 1fr;gap:6px 14px;font-size:13.5px;margin-bottom:16px;}
.inspector .kv dt{color:var(--ink-3);font-size:12px;letter-spacing:.04em;text-transform:uppercase;}
.inspector .kv dd{margin:0;font-family:var(--mono);font-size:13px;}
.chain{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-top:16px;font-family:var(--mono);font-size:12.5px;}
.chain .link{border:1px solid var(--line);border-radius:8px;padding:5px 11px;background:#fff;}
.chain .link.on{border-color:var(--accent);background:var(--accent-soft);color:#004b96;font-weight:700;}
.chain .arw{color:var(--ink-3);}

.preview-mini{border:1px solid var(--line);border-radius:12px;background:var(--bg-2);padding:16px;}
.preview-mini .screen{background:#fff;border:1px solid var(--line-soft);border-radius:10px;padding:12px;min-height:168px;}

/* ---------- Demo 04 · gravity ---------- */
.glab{display:grid;grid-template-columns:1fr 1fr;gap:22px;}
.gcard{border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:20px;display:flex;flex-direction:column;}
.gcard h4{margin:0 0 3px;font-size:16.5px;letter-spacing:-.01em;}
.gcard .attr{font-family:var(--mono);font-size:12.5px;color:var(--accent);margin-bottom:14px;}
.gcard .scope{font-size:13px;color:var(--ink-3);margin-bottom:14px;line-height:1.45;}
.frame{
  flex:1;border:1px dashed var(--line);border-radius:10px;background:var(--bg-2);
  padding:10px;display:flex;min-height:160px;transition:.22s;
}
.frame .box{
  background:var(--accent-soft);border:1px solid rgba(0,102,204,.35);border-radius:8px;
  padding:10px 12px;font-size:12.5px;color:#004b96;text-align:left;transition:.22s;
  display:flex;flex-direction:column;gap:2px;justify-content:flex-start;
}
.frame .box .t{font-weight:620;}
.frame .box .s{font-size:11px;opacity:.75;}
.attrout{margin-top:20px;}

/* 3 x 3 position picker */
.posgrid{display:grid;grid-template-columns:repeat(3,1fr);gap:6px;margin-top:16px;}
.posgrid button{
  font:inherit;font-size:11.5px;padding:9px 4px;border:1px solid var(--line);border-radius:8px;
  background:#fff;color:var(--ink-2);cursor:pointer;transition:.14s;line-height:1.25;
}
.posgrid button:hover{border-color:var(--ink-3);}
.posgrid button.on{background:var(--accent);border-color:var(--accent);color:#fff;font-weight:600;}

/* overlapping layers (FrameLayout) */
.overlap{position:relative;border:1px solid var(--line);border-radius:12px;overflow:hidden;height:300px;background:var(--bg-3);}
.overlap img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;transition:opacity .25s;}
.overlap .ov{
  position:absolute;left:0;right:0;bottom:0;padding:26px 26px 24px;
  background:linear-gradient(to top,rgba(12,12,14,.82),rgba(12,12,14,0));color:#fff;transition:.25s;
}
.overlap .ov .big{font-size:26px;font-weight:660;letter-spacing:-.02em;line-height:1.15;}
.overlap .ov .sm{font-size:14px;color:rgba(255,255,255,.8);margin-top:5px;}
.overlap.hide-img img{opacity:0;}
.overlap.hide-text .ov{opacity:0;transform:translateY(8px);}
.layerbtns{display:flex;gap:9px;flex-wrap:wrap;margin-top:16px;}

/* FrameLayout stacking demo */
.stackgrid{display:grid;grid-template-columns:300px 1fr;gap:32px;align-items:start;}
.flayers{border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:16px;}
.flayer{
  display:flex;align-items:center;gap:12px;padding:10px 12px;border-radius:9px;border:1px solid var(--line-soft);
  margin-bottom:8px;font-size:13.5px;cursor:pointer;transition:.16s;background:#fff;
}
.flayer:last-child{margin-bottom:0;}
.flayer:hover{border-color:var(--ink-3);}
.flayer.on{border-color:var(--accent);background:var(--accent-soft);}
.flayer .sw{width:26px;height:18px;border-radius:4px;border:1px solid var(--line);flex:0 0 26px;}
.flayer .nm{font-family:var(--mono);font-size:12.5px;}
.flayer .idx{margin-left:auto;font-size:11px;color:var(--ink-3);}
.stackprev{
  position:relative;border:1px solid var(--line);border-radius:12px;background:var(--bg-2);
  height:250px;overflow:hidden;
}
.stackprev .layer{
  position:absolute;left:24px;right:24px;border-radius:10px;border:1px solid rgba(0,102,204,.35);
  background:rgba(233,241,251,.92);padding:12px 16px;font-size:13px;color:#004b96;transition:.24s;
}

/* ---------- index page ---------- */
.hero{padding:96px 0 60px;border-bottom:1px solid var(--line-soft);}
.hero .eyebrow{font-size:13px;letter-spacing:.14em;text-transform:uppercase;color:var(--accent);font-weight:600;margin:0 0 18px;}
.hero h1{font-size:clamp(38px,5.4vw,62px);line-height:1.06;letter-spacing:-.025em;font-weight:680;margin:0 0 20px;}
.hero p.lede{font-size:21px;color:var(--ink-2);max-width:64ch;margin:0;}
.hero .meta{margin-top:30px;font-size:14px;color:var(--ink-3);}
.idx-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(430px,1fr));gap:24px;padding:64px 0 40px;}
.idx-card{
  border:1px solid var(--line);border-radius:18px;background:#fff;text-decoration:none;color:var(--ink);
  padding:30px 32px 26px;display:flex;flex-direction:column;transition:.18s;
}
.idx-card:hover{border-color:var(--ink-3);transform:translateY(-2px);box-shadow:0 14px 34px rgba(0,0,0,.07);}
.idx-card .top{display:flex;align-items:flex-start;gap:22px;}
.idx-card .thumb{width:96px;flex:0 0 96px;height:120px;overflow:hidden;border-radius:12px;background:var(--bg-2);display:block;padding:0;}
.idx-card .thumb img{width:100%;height:100%;object-fit:cover;display:block;transition:transform .35s ease;}
.idx-card:hover .thumb img{transform:scale(1.04);}
.idx-card .no{font-family:var(--mono);font-size:12px;color:var(--accent);letter-spacing:.1em;}
.idx-card h2{font-size:25px;letter-spacing:-.018em;margin:4px 0 8px;font-weight:660;line-height:1.15;}
.idx-card .why{font-size:14.5px;color:var(--ink-2);margin:0;}
.idx-card .foot{margin-top:22px;padding-top:16px;border-top:1px solid var(--line-soft);display:flex;align-items:center;justify-content:space-between;font-size:13px;color:var(--ink-3);}
.idx-card .foot .open{font-weight:600;color:var(--accent);}
.tips{padding:20px 0 90px;}
.tips .box{border:1px solid var(--line);border-radius:var(--radius);background:var(--bg-2);padding:24px 28px;}
.tips ul{margin:10px 0 0;padding-left:20px;font-size:15.5px;color:var(--ink-2);line-height:1.7;}
footer{padding:40px 0 70px;color:var(--ink-3);font-size:13.5px;border-top:1px solid var(--line-soft);}
footer .wrap{display:flex;justify-content:space-between;flex-wrap:wrap;gap:14px;}

@media (max-width:1000px){
  .grid{grid-template-columns:1fr;gap:32px;}
  .side{position:static;}
  .wrap,.nav-inner{padding:0 24px;}
  .idx-grid{grid-template-columns:1fr;}
  .life-cols,.glab,.stackgrid{grid-template-columns:1fr;}
  .stage{padding:24px 12px;}
}