/* morse.hansda.in — PCB / instrument aesthetic
   Grounded in the reference device: matte black board, white silkscreen,
   green trace LEDs for the live path, red LED for the resolved letter. */

:root{
  /* surface */
  --pcb:        #0b0e0d;
  --pcb-2:      #111614;
  --pcb-3:      #171d1b;
  --solder:     #1f2624;
  --edge:       #2b3431;
  /* silkscreen */
  --silk:       #e8ece9;
  --silk-dim:   #7e8a86;
  --silk-faint: #4a534f;
  /* LEDs */
  --led-green:  #2bff88;
  --led-green-d:#0d5c33;
  --led-red:    #ff3b3b;
  --led-red-d:  #5c1010;
  --led-amber:  #ffb03a;
  /* type */
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", "DejaVu Sans Mono", Menlo, monospace;
  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  /* rhythm */
  --r-sm: 6px; --r-md: 12px; --r-lg: 20px;
  --sp: 16px;
  --gap-sec: 48px;
  --tap: 44px;
}

*,*::before,*::after{ box-sizing:border-box; }

html{ -webkit-text-size-adjust:100%; }

body{
  margin:0;
  min-height:100vh;
  background:
    radial-gradient(1200px 700px at 50% -10%, #14201c 0%, transparent 60%),
    repeating-linear-gradient(0deg, rgba(255,255,255,.012) 0 1px, transparent 1px 3px),
    var(--pcb);
  color:var(--silk);
  font-family:var(--sans);
  font-size:16px;
  line-height:1.55;
  letter-spacing:.01em;
}

a{ color:var(--led-green); text-decoration:none; }
a:hover{ text-decoration:underline; }
:focus-visible{ outline:2px solid var(--led-green); outline-offset:3px; border-radius:4px; }

.skip{
  position:absolute; left:-9999px; top:0; z-index:100;
  background:var(--led-green); color:#04150c; padding:10px 16px; border-radius:0 0 var(--r-sm) 0;
  font-weight:700;
}
.skip:focus{ left:0; }

.wrap{ width:min(1240px, 100% - 32px); margin-inline:auto; }

/* ── header ─────────────────────────────────────────────────────── */
.site-head{
  border-bottom:1px solid var(--edge);
  background:linear-gradient(180deg, rgba(43,255,136,.05), transparent 70%), var(--pcb-2);
  position:sticky; top:0; z-index:30;
  backdrop-filter:blur(8px);
}
.head-in{ display:flex; align-items:center; gap:14px; padding:12px 0; }
.brand{ display:flex; align-items:center; gap:10px; font-family:var(--mono); }
.brand .mark{
  width:30px; height:30px; flex:none;
  border:1px solid var(--edge); border-radius:var(--r-sm);
  display:grid; place-items:center; background:var(--pcb-3);
}
.brand b{ letter-spacing:.22em; font-size:13px; font-weight:700; text-transform:uppercase; }
.brand span{ color:var(--silk-faint); font-size:11px; letter-spacing:.18em; display:block; }
.head-sp{ margin-left:auto; }

.tabs{ display:flex; gap:4px; }
.tab{
  font-family:var(--mono); font-size:12px; letter-spacing:.12em; text-transform:uppercase;
  background:transparent; color:var(--silk-dim); border:1px solid transparent;
  padding:9px 14px; min-height:var(--tap); border-radius:var(--r-sm); cursor:pointer;
}
.tab[aria-selected="true"]{ color:var(--led-green); border-color:var(--led-green-d); background:rgba(43,255,136,.07); }

.hamb{ display:none; background:var(--pcb-3); border:1px solid var(--edge); color:var(--silk);
  width:var(--tap); height:var(--tap); border-radius:var(--r-sm); cursor:pointer; font-size:18px; }

/* ── layout ─────────────────────────────────────────────────────── */
main{ padding:28px 0 80px; }
.panel{ display:none; }
.panel.on{ display:block; }

.grid{ display:grid; gap:20px; grid-template-columns:1fr; }
/* Grid/flex children default to min-width:auto, which refuses to shrink below
   their content. Without this the tree's horizontal scroll container pushes the
   whole page wider than the viewport on a phone (measured 666px at 390px). */
.grid > *{ min-width:0; }
@media (min-width:1024px){ .grid.split{ grid-template-columns:1fr 380px; align-items:start; } }

.card{
  background:linear-gradient(180deg, var(--pcb-3), var(--pcb-2));
  border:1px solid var(--edge);
  border-radius:var(--r-lg);
  padding:20px;
  position:relative;
}
.card::before{
  content:''; position:absolute; inset:8px; border:1px dashed rgba(232,236,233,.06);
  border-radius:calc(var(--r-lg) - 8px); pointer-events:none;
}
.card > *{ position:relative; }
.card h2{
  margin:0 0 14px; font-family:var(--mono); font-size:12px; font-weight:600;
  letter-spacing:.22em; text-transform:uppercase; color:var(--silk-dim);
  display:flex; align-items:center; gap:10px;
}
.card h2::after{ content:''; flex:1; height:1px; background:var(--edge); }

/* ── the tree ───────────────────────────────────────────────────── */
.tree-wrap{ overflow-x:auto; overflow-y:hidden; -webkit-overflow-scrolling:touch; padding-bottom:6px; }
#tree{ display:block; width:100%; min-width:760px; height:auto; }
.tw-edge{ stroke:var(--silk-faint); stroke-width:1.6; fill:none; opacity:.5; }
.tw-edge.hot{ stroke:var(--led-green); opacity:1; stroke-width:3; filter:drop-shadow(0 0 5px var(--led-green)); }
.tw-node circle{ fill:var(--solder); stroke:var(--edge); stroke-width:1; transition:fill .09s linear, stroke .09s linear; }
.tw-node text{ fill:var(--silk); font-family:var(--mono); font-size:17px; font-weight:700; text-anchor:middle; dominant-baseline:central; }
.tw-node.lit circle{ fill:var(--led-green); stroke:var(--led-green); filter:drop-shadow(0 0 6px var(--led-green)); }
.tw-node.lit text{ fill:#04150c; }
.tw-node.hit circle{ fill:var(--led-red); stroke:var(--led-red); filter:drop-shadow(0 0 9px var(--led-red)); }
.tw-node.hit text{ fill:#fff; }
.tw-node.play circle{ fill:var(--led-red); stroke:var(--led-red); filter:drop-shadow(0 0 8px var(--led-red)); }

/* ── readout ────────────────────────────────────────────────────── */
.readout{
  display:grid; gap:12px;
  grid-template-columns:auto 1fr;
  align-items:center;
  background:var(--pcb); border:1px solid var(--edge); border-radius:var(--r-md);
  padding:14px 16px; margin-bottom:16px;
}
.big-letter{
  font-family:var(--mono); font-size:56px; font-weight:700; line-height:1;
  width:76px; text-align:center; color:var(--led-amber);
  text-shadow:0 0 18px rgba(255,176,58,.45);
}
.big-letter.none{ color:var(--silk-faint); text-shadow:none; opacity:.5; }
.sym-live{ font-family:var(--mono); font-size:26px; letter-spacing:.18em; color:var(--led-green); min-height:34px; word-break:break-all; }
.sym-hint{ font-family:var(--mono); font-size:11px; letter-spacing:.14em; color:var(--silk-faint); text-transform:uppercase; }

.tape{
  font-family:var(--mono); font-size:20px; letter-spacing:.06em;
  background:var(--pcb); border:1px solid var(--edge); border-radius:var(--r-md);
  padding:14px 16px; min-height:64px; word-break:break-word; white-space:pre-wrap;
  color:var(--silk);
}
.tape:empty::before{ content:attr(data-empty); color:var(--silk-faint); }

/* live position while a message plays back, and the prediction still resolving */
.tp-now{
  color:var(--led-red);
  text-shadow:0 0 12px rgba(255,59,59,.55);
  font-weight:700;
}
.tp-pending{
  color:var(--led-amber);
  opacity:.85;
  border-bottom:2px solid var(--led-amber);
}

/* ── key / buttons ──────────────────────────────────────────────── */
.keys{ display:grid; grid-template-columns:1fr 1fr; gap:12px; margin-top:16px; }
.key{
  font-family:var(--mono); font-size:15px; letter-spacing:.14em; text-transform:uppercase;
  min-height:76px; border-radius:var(--r-md); cursor:pointer;
  background:linear-gradient(180deg,#202825,#161d1b);
  border:1px solid var(--edge); color:var(--silk);
  user-select:none; -webkit-user-select:none; touch-action:manipulation;
  transition:transform .05s ease, box-shadow .1s ease, border-color .1s ease;
}
.key:active,.key.down{
  transform:translateY(2px);
  border-color:var(--led-green); color:var(--led-green);
  box-shadow:inset 0 0 22px rgba(43,255,136,.22);
}
.key.wide{ grid-column:1/-1; min-height:96px; font-size:17px; }
.key small{ display:block; font-size:10px; letter-spacing:.1em; color:var(--silk-faint); margin-top:6px; }

.btn-row{ display:flex; flex-wrap:wrap; gap:8px; margin-top:12px; }
.btn{
  font-family:var(--mono); font-size:12px; letter-spacing:.12em; text-transform:uppercase;
  background:var(--pcb-3); border:1px solid var(--edge); color:var(--silk-dim);
  padding:0 16px; min-height:var(--tap); border-radius:var(--r-sm); cursor:pointer;
}
.btn:hover{ color:var(--silk); border-color:var(--silk-faint); }
.btn.primary{ background:rgba(43,255,136,.1); border-color:var(--led-green-d); color:var(--led-green); }
.btn.danger:hover{ color:var(--led-red); border-color:var(--led-red-d); }
.btn[aria-pressed="true"]{ background:rgba(43,255,136,.14); border-color:var(--led-green); color:var(--led-green); }

/* ── controls ───────────────────────────────────────────────────── */
.ctl{ display:grid; gap:6px; margin-bottom:16px; }
.ctl label{ font-family:var(--mono); font-size:11px; letter-spacing:.14em; text-transform:uppercase; color:var(--silk-dim); display:flex; justify-content:space-between; }
.ctl label b{ color:var(--led-green); font-weight:600; }
input[type=range]{ width:100%; accent-color:var(--led-green); height:var(--tap); }

textarea, input[type=text]{
  width:100%; background:var(--pcb); color:var(--silk);
  border:1px solid var(--edge); border-radius:var(--r-md);
  padding:12px 14px; font-family:var(--mono); font-size:16px; line-height:1.5;
  resize:vertical;
}
textarea:focus, input[type=text]:focus{ border-color:var(--led-green); outline:none; }

/* ── chart ──────────────────────────────────────────────────────── */
.chart{ display:grid; grid-template-columns:repeat(2,1fr); gap:8px; }
@media (min-width:640px){ .chart{ grid-template-columns:repeat(4,1fr); } }
@media (min-width:1024px){ .chart{ grid-template-columns:repeat(6,1fr); } }
.chip{
  display:flex; align-items:center; gap:10px;
  background:var(--pcb); border:1px solid var(--edge); border-radius:var(--r-sm);
  padding:8px 10px; min-height:var(--tap); cursor:pointer; text-align:left;
  color:var(--silk); font-family:var(--mono);
}
.chip b{ font-size:17px; width:1.4em; flex:none; }
.chip span{ font-size:13px; letter-spacing:.14em; color:var(--led-green); }
.chip.play{ border-color:var(--led-red); box-shadow:0 0 14px rgba(255,59,59,.3); }

/* ── trainer ────────────────────────────────────────────────────── */
.quiz-target{ font-family:var(--mono); font-size:72px; text-align:center; color:var(--led-amber); line-height:1.1; margin:6px 0 2px; }
.quiz-sub{ text-align:center; font-family:var(--mono); font-size:12px; letter-spacing:.2em; color:var(--silk-faint); text-transform:uppercase; }
.score{ display:flex; gap:18px; justify-content:center; font-family:var(--mono); font-size:12px; letter-spacing:.14em; color:var(--silk-dim); margin-top:14px; }
.score b{ color:var(--led-green); }
.verdict{ text-align:center; font-family:var(--mono); letter-spacing:.16em; min-height:24px; margin-top:10px; text-transform:uppercase; font-size:13px; }
.verdict.ok{ color:var(--led-green); }
.verdict.no{ color:var(--led-red); }

/* ── misc ───────────────────────────────────────────────────────── */
.hint{ font-size:13px; color:var(--silk-dim); margin:10px 0 0; }
kbd{
  font-family:var(--mono); font-size:11px; background:var(--pcb); border:1px solid var(--edge);
  border-bottom-width:2px; border-radius:4px; padding:2px 6px; color:var(--silk);
}
.site-foot{ border-top:1px solid var(--edge); padding:24px 0 40px; color:var(--silk-faint); font-size:13px; }
.site-foot p{ margin:.3em 0; }

/* ── responsive ─────────────────────────────────────────────────── */
@media (max-width:1023px){
  main{ padding:20px 0 64px; }
  :root{ --gap-sec:64px; }
}
@media (max-width:639px){
  :root{ --gap-sec:48px; }
  .wrap{ width:calc(100% - 24px); }
  .head-sp{ display:none; }
  .hamb{ display:block; margin-left:auto; }
  .tabs{
    display:none; position:absolute; top:100%; left:0; right:0;
    flex-direction:column; gap:0; background:var(--pcb-2);
    border-bottom:1px solid var(--edge); padding:8px;
  }
  .tabs.open{ display:flex; }
  .tab{ text-align:left; width:100%; }
  .big-letter{ font-size:44px; width:58px; }
  .sym-live{ font-size:20px; }
  .quiz-target{ font-size:56px; }
  .card{ padding:16px; border-radius:var(--r-md); }
  #tree{ min-width:760px; }
}

@media (hover:none){
  .key:hover{ transform:none; }
}
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{ transition:none !important; animation:none !important; }
}