@import url('https://fonts.googleapis.com/css2?family=Rajdhani:wght@500;600;700&family=JetBrains+Mono:wght@400;600&display=swap');

:root {
  --bg: #0d0d0d;
  --surface: rgba(20, 20, 20, 0.95);
  --border: rgba(0, 255, 136, 0.15);
  --accent: #00ff88;
  --accent-dim: rgba(0, 255, 136, 0.08);
  --text: #e0e0e0;
  --muted: #666;
  --radius: 10px;
  --glow: 0 0 18px rgba(0, 255, 136, 0.12);

  /* operator colors */
  --col-exp:     #ff4f4f;
  --col-muldiv:  #ffb300;
  --col-addsub:  #4fc3f7;
  --col-operand: #00ff88;
  --col-paren:   #888;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: 'JetBrains Mono', monospace;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

#tsparticles { position: fixed; inset: 0; z-index: 0; }

.app {
  position: relative;
  z-index: 1;
  padding: 30px 24px 50px;
  max-width: 980px;
  margin: 0 auto;
}

h1 {
  text-align: center;
  font-family: 'Rajdhani', sans-serif;
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 2px;
  text-shadow: 0 0 24px rgba(0, 255, 136, 0.35);
  margin-bottom: 28px;
}

.main-content { display: flex; flex-direction: column; }
.content { display: flex; flex-direction: column; gap: 14px; }

/* ── Controls ── */
.controls {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  box-shadow: var(--glow);
}

.controls label { font-size: 12px; color: var(--muted); letter-spacing: 1px; }

select, input[type="text"] {
  background: #1a1a1a;
  border: 1px solid rgba(0, 255, 136, 0.2);
  border-radius: 6px;
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  padding: 7px 11px;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

select:focus, input[type="text"]:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(0, 255, 136, 0.08);
}

input[type="text"] { min-width: 200px; }
input[type="text"]::placeholder { color: var(--muted); }

input[type="range"] {
  -webkit-appearance: none;
  width: 90px;
  height: 4px;
  border-radius: 99px;
  background: #2a2a2a;
  outline: none;
  cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid #0d0d0d;
  box-shadow: 0 0 7px rgba(0, 255, 136, 0.6);
  cursor: pointer;
  transition: transform 0.15s;
}
input[type="range"]::-webkit-slider-thumb:hover { transform: scale(1.2); }

#speedLabel { font-size: 12px; color: var(--accent); min-width: 28px; }

button {
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  font-weight: 600;
  padding: 7px 14px;
  border-radius: 6px;
  border: 1px solid transparent;
  cursor: pointer;
  letter-spacing: 0.5px;
  transition: all 0.18s;
}

#btnStart {
  background: var(--accent);
  color: #0d0d0d;
  border-color: var(--accent);
}
#btnStart:hover {
  background: #33ffaa;
  box-shadow: 0 0 14px rgba(0, 255, 136, 0.45);
}

#btnReset {
  background: #1a1a1a;
  color: var(--text);
  border-color: rgba(0, 255, 136, 0.2);
}
#btnReset:hover { border-color: var(--accent); color: var(--accent); }

#pauseBtn {
  background: #1a1a1a;
  color: var(--text);
  border-color: rgba(0, 255, 136, 0.2);
}
#pauseBtn:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
#pauseBtn:disabled { opacity: 0.35; cursor: not-allowed; }

#btnPrecedence {
  background: transparent;
  color: var(--accent);
  border-color: rgba(0, 255, 136, 0.35);
}
#btnPrecedence:hover {
  background: var(--accent-dim);
  box-shadow: 0 0 10px rgba(0, 255, 136, 0.15);
}

/* ── Precedence Sidebar ── */
.sidebar {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: var(--glow);
  display: none;
  animation: fadeSlide 0.2s ease-out;
}

.sidebar.open { display: block; }

@keyframes fadeSlide {
  from { opacity: 0; transform: translateY(-6px); }
  to   { opacity: 1; transform: translateY(0); }
}

.sidebar h3 {
  font-family: 'Rajdhani', sans-serif;
  font-size: 1rem;
  color: var(--accent);
  letter-spacing: 1px;
  margin-bottom: 10px;
}

.sidebar p { font-size: 12px; color: var(--muted); line-height: 1.6; margin-bottom: 12px; }

.precedence-table { display: flex; flex-direction: column; gap: 8px; margin-bottom: 14px; }

.precedence-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #1a1a1a;
  border: 1px solid rgba(0, 255, 136, 0.1);
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 12px;
}

.precedence-row:nth-child(1) { border-left: 3px solid var(--col-exp); }
.precedence-row:nth-child(2) { border-left: 3px solid var(--col-muldiv); }
.precedence-row:nth-child(3) { border-left: 3px solid var(--col-addsub); }

.precedence-row .op { color: var(--text); }
.precedence-row .prec { font-weight: 600; font-size: 11px; }
.precedence-row:nth-child(1) .prec { color: var(--col-exp); }
.precedence-row:nth-child(2) .prec { color: var(--col-muldiv); }
.precedence-row:nth-child(3) .prec { color: var(--col-addsub); }

.note {
  background: rgba(0, 255, 136, 0.05);
  border: 1px solid rgba(0, 255, 136, 0.12);
  border-radius: 6px;
  padding: 10px 12px;
  font-size: 11px;
  color: #aaa;
  line-height: 1.7;
  margin-bottom: 12px;
}

.close-btn {
  width: 100%;
  background: #1a1a1a !important;
  color: var(--text) !important;
  border: 1px solid rgba(0, 255, 136, 0.2) !important;
}
.close-btn:hover { border-color: var(--accent) !important; color: var(--accent) !important; }

/* ── Info Bar ── */
.info {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  padding: 11px 16px;
  font-size: 13px;
}

/* ── Visual Section ── */
.visual-section {
  display: flex;
  gap: 16px;
}

.visual-section > div {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: var(--glow);
}

.visual-section > div:first-child { flex: 1; }
.visual-section > div:last-child  { flex: 2; }

.visual-section h3 {
  font-family: 'Rajdhani', sans-serif;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 2px;
  color: var(--accent);
  opacity: 0.75;
  margin-bottom: 14px;
  text-transform: uppercase;
}

/* ── Stack ── */
.stack-container {
  display: flex;
  flex-direction: column;
  gap: 8px;                         /* gap between items so they look separate */
  min-height: 200px;
  justify-content: flex-end;
  background: #0f0f0f;
  border: 1px solid rgba(255,255,255,0.06);
  border-bottom: 3px solid rgba(0, 255, 136, 0.4);
  border-radius: 8px 8px 4px 4px;
  padding: 10px 10px 0 10px;
  position: relative;
}

/* "BOTTOM" label */
.stack-container::after {
  content: '▬ BASE ▬';
  display: block;
  text-align: center;
  font-size: 9px;
  letter-spacing: 3px;
  color: rgba(0, 255, 136, 0.3);
  padding: 6px 0 8px;
}

.stack-item {
  border-radius: 8px;               /* full radius now — not connected */
  padding: 14px 18px;               /* bigger padding = taller items */
  font-size: 26px;                  /* larger symbol */
  font-weight: 700;
  text-align: center;
  border: 1px solid transparent;
  animation: stackPush 0.22s cubic-bezier(0.34, 1.56, 0.64, 1);
  transition: all 0.2s;
  position: relative;
}

/* stacked look — each item slightly indented */
.stack-item::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: rgba(255,255,255,0.02);
}

/* color by operator type */
.stack-item.op-exp    { background: rgba(255, 79, 79, 0.12);  border-color: rgba(255, 79, 79, 0.35);  color: var(--col-exp);     box-shadow: inset 0 1px 0 rgba(255,79,79,0.2); }
.stack-item.op-muldiv { background: rgba(255,179, 0, 0.12);  border-color: rgba(255,179, 0, 0.35);  color: var(--col-muldiv);  box-shadow: inset 0 1px 0 rgba(255,179,0,0.2); }
.stack-item.op-addsub { background: rgba(79,195,247, 0.12);  border-color: rgba(79,195,247, 0.35);  color: var(--col-addsub);  box-shadow: inset 0 1px 0 rgba(79,195,247,0.2); }
.stack-item.op-paren  { background: rgba(136,136,136,0.1);   border-color: rgba(136,136,136,0.25);  color: var(--col-paren);   box-shadow: none; }
.stack-item.op-operand{ background: rgba(0,255,136, 0.1);    border-color: rgba(0,255,136, 0.3);    color: var(--col-operand); box-shadow: inset 0 1px 0 rgba(0,255,136,0.15); }

@keyframes stackPush {
  from { transform: translateY(-16px) scaleX(0.85); opacity: 0; }
  to   { transform: translateY(0)     scaleX(1);    opacity: 1; }
}

/* ── Output ── */
.output-box {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  min-height: 200px;
  align-content: flex-start;
}

.output-token {
  border-radius: 6px;
  padding: 9px 16px;
  font-size: 18px;
  font-weight: 700;
  border: 1px solid transparent;
  animation: popIn 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.output-token.op-exp     { background: rgba(255, 79, 79, 0.12); border-color: rgba(255, 79, 79, 0.35); color: var(--col-exp); }
.output-token.op-muldiv  { background: rgba(255,179, 0, 0.12);  border-color: rgba(255,179, 0, 0.35);  color: var(--col-muldiv); }
.output-token.op-addsub  { background: rgba(79,195,247, 0.12);  border-color: rgba(79,195,247, 0.35);  color: var(--col-addsub); }
.output-token.op-operand { background: rgba(0,255,136, 0.1);    border-color: rgba(0,255,136, 0.3);    color: var(--col-operand); }

@keyframes popIn {
  from { transform: scale(0.7); opacity: 0; }
  to   { transform: scale(1);   opacity: 1; }
}

/* ── Responsive ── */
@media (max-width: 640px) {
  .visual-section { flex-direction: column; }
  .controls { gap: 8px; }
  input[type="text"] { min-width: 140px; }
}