:root {
  --bg: #0a0a0f;
  --surface: #12121a;
  --surface-2: #1a1a2e;
  --grid: #1a1a2e;
  --pink: #ff2d6a;
  --cyan: #00f0ff;
  --purple: #bf00ff;
  --mint: #39ff14;
  --error: #ff3366;
  --text: #e8e8f0;
  --muted: #6b6b8a;

  --glow-pink: 0 0 6px #ff2d6a, 0 0 14px rgba(255, 45, 106, 0.6), 0 0 28px rgba(255, 45, 106, 0.3);
  --glow-cyan: 0 0 6px #00f0ff, 0 0 14px rgba(0, 240, 255, 0.6), 0 0 28px rgba(0, 240, 255, 0.3);
  --glow-purple: 0 0 6px #bf00ff, 0 0 14px rgba(191, 0, 255, 0.6), 0 0 28px rgba(191, 0, 255, 0.3);
  --glow-mint: 0 0 6px #39ff14, 0 0 16px rgba(57, 255, 20, 0.6), 0 0 36px rgba(57, 255, 20, 0.35);
  --glow-error: 0 0 6px #ff3366, 0 0 14px rgba(255, 51, 102, 0.7);
}

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

html, body {
  background: var(--bg);
  color: var(--text);
  font-family: "IBM Plex Sans", system-ui, sans-serif;
  min-height: 100vh;
  overflow-x: hidden;
}

body {
  position: relative;
  padding-bottom: 60px;
}

/* CRT scanlines overlay */
.scanlines {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom,
    rgba(255, 255, 255, 0.02) 0,
    rgba(255, 255, 255, 0.02) 1px,
    transparent 1px,
    transparent 3px
  );
  z-index: 9999;
  mix-blend-mode: overlay;
}

/* Grid background */
.grid-bg {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 32px 32px;
  opacity: 0.5;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 90%);
  z-index: 0;
}

/* Topbar */
.topbar {
  position: relative;
  z-index: 2;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 24px;
  border-bottom: 1px solid var(--grid);
  background: rgba(10, 10, 15, 0.75);
  backdrop-filter: blur(6px);
}

.logo {
  font-family: "Orbitron", "Space Mono", monospace;
  font-weight: 900;
  font-size: 18px;
  letter-spacing: 3px;
  color: var(--cyan);
  text-shadow: var(--glow-cyan);
  display: flex;
  align-items: center;
  gap: 8px;
}
.logo-bracket { color: var(--purple); text-shadow: var(--glow-purple); }
.logo-accent { color: var(--pink); text-shadow: var(--glow-pink); }
.logo-sub {
  font-family: "JetBrains Mono", monospace;
  font-size: 10px;
  letter-spacing: 1px;
  color: var(--muted);
  text-shadow: none;
  margin-left: 6px;
}

.install-btn {
  background: transparent;
  color: var(--mint);
  border: 1px solid var(--mint);
  padding: 6px 14px;
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
  letter-spacing: 2px;
  cursor: pointer;
  box-shadow: var(--glow-mint);
  text-shadow: 0 0 4px var(--mint);
  transition: transform 0.15s;
}
.install-btn:hover { transform: scale(1.05); }

.topbar-actions {
  display: flex;
  align-items: center;
  gap: 10px;
}

.share-btn {
  background: transparent;
  color: var(--pink);
  border: 1px solid var(--pink);
  padding: 6px 14px;
  font-family: "Space Mono", "JetBrains Mono", monospace;
  font-weight: 700;
  font-size: 12px;
  letter-spacing: 2px;
  cursor: pointer;
  box-shadow: var(--glow-pink), inset 0 0 8px rgba(255, 0, 128, 0.15);
  text-shadow: 0 0 4px var(--pink);
  transition: transform 0.15s, color 0.15s, border-color 0.15s, box-shadow 0.15s, text-shadow 0.15s;
}
.share-btn:hover:not(:disabled) {
  color: var(--cyan);
  border-color: var(--cyan);
  box-shadow: var(--glow-cyan), inset 0 0 12px rgba(0, 255, 255, 0.2);
  text-shadow: 0 0 6px var(--cyan);
  transform: scale(1.05);
}
.share-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  box-shadow: none;
  text-shadow: none;
}
.share-btn.copied {
  color: var(--mint);
  border-color: var(--mint);
  box-shadow: var(--glow-mint), inset 0 0 12px rgba(0, 255, 170, 0.2);
  text-shadow: 0 0 6px var(--mint);
}

/* Container */
.container {
  position: relative;
  z-index: 1;
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 20px;
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.section-label {
  display: block;
  font-family: "JetBrains Mono", monospace;
  font-size: 11px;
  letter-spacing: 3px;
  color: var(--cyan);
  text-shadow: 0 0 4px rgba(0, 240, 255, 0.5);
  margin-bottom: 10px;
  text-transform: uppercase;
}

/* Input */
.input-section {
  padding: 20px;
  background: var(--surface);
  border: 1px solid var(--grid);
  border-radius: 4px;
  position: relative;
}

.input-wrap {
  position: relative;
  display: flex;
  align-items: center;
  background: var(--bg);
  border: 1px solid var(--purple);
  border-radius: 3px;
  padding: 14px 16px;
  box-shadow: 0 0 0 rgba(191, 0, 255, 0);
  transition: box-shadow 0.2s, border-color 0.2s;
}
.input-wrap:focus-within {
  border-color: var(--cyan);
  box-shadow: var(--glow-cyan);
}
.input-wrap.error {
  border-color: var(--error);
  box-shadow: var(--glow-error);
  animation: shake 0.4s ease;
}

.input-prompt {
  font-family: "JetBrains Mono", monospace;
  color: var(--mint);
  font-weight: 700;
  margin-right: 10px;
  text-shadow: 0 0 6px var(--mint);
}

#expr {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--pink);
  font-family: "JetBrains Mono", monospace;
  font-size: 22px;
  letter-spacing: 1px;
  text-shadow: var(--glow-pink);
  caret-color: var(--cyan);
}
#expr::placeholder { color: var(--muted); text-shadow: none; opacity: 0.6; }

.error-msg {
  min-height: 18px;
  margin-top: 10px;
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
  color: var(--error);
  text-shadow: 0 0 6px rgba(255, 51, 102, 0.8);
  letter-spacing: 1px;
}

.actions {
  display: flex;
  gap: 10px;
  margin-top: 16px;
}

.btn {
  font-family: "JetBrains Mono", monospace;
  font-size: 13px;
  letter-spacing: 2px;
  padding: 10px 20px;
  border-radius: 3px;
  cursor: pointer;
  background: transparent;
  transition: transform 0.15s, box-shadow 0.2s;
  text-transform: uppercase;
}
.btn-sm { padding: 6px 12px; font-size: 11px; }

.btn-primary {
  border: 1px solid var(--cyan);
  color: var(--cyan);
  text-shadow: 0 0 6px var(--cyan);
  box-shadow: 0 0 6px rgba(0, 240, 255, 0.3), inset 0 0 12px rgba(0, 240, 255, 0.05);
}
.btn-primary:hover:not(:disabled) {
  box-shadow: var(--glow-cyan), inset 0 0 12px rgba(0, 240, 255, 0.1);
  transform: scale(1.03);
}
.btn-primary:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.btn-ghost {
  border: 1px solid var(--muted);
  color: var(--muted);
}
.btn-ghost:hover {
  border-color: var(--pink);
  color: var(--pink);
  text-shadow: 0 0 6px var(--pink);
}

/* Tokens */
.tokens-section, .steps-section, .history-section {
  position: relative;
}
.tokens-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 14px;
  background: var(--surface);
  border: 1px dashed var(--grid);
  border-radius: 4px;
  min-height: 70px;
  align-items: center;
}

.token {
  font-family: "JetBrains Mono", monospace;
  padding: 8px 14px;
  border-radius: 3px;
  background: var(--bg);
  border: 1px solid currentColor;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  font-size: 16px;
  font-weight: 700;
  animation: pop-in 0.25s ease-out backwards;
}
.token-label {
  font-size: 8px;
  letter-spacing: 2px;
  font-weight: 400;
  opacity: 0.7;
}

.token.number { color: var(--pink); box-shadow: 0 0 8px rgba(255, 45, 106, 0.5); text-shadow: 0 0 6px var(--pink); }
.token.operator { color: var(--cyan); box-shadow: 0 0 8px rgba(0, 240, 255, 0.5); text-shadow: 0 0 6px var(--cyan); }
.token.paren { color: var(--purple); box-shadow: 0 0 8px rgba(191, 0, 255, 0.5); text-shadow: 0 0 6px var(--purple); }

/* Steps */
.steps-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.step-card {
  background: var(--surface);
  border-left: 3px solid var(--cyan);
  border-top: 1px solid var(--grid);
  border-right: 1px solid var(--grid);
  border-bottom: 1px solid var(--grid);
  padding: 14px 18px;
  border-radius: 3px;
  position: relative;
  animation: slide-in 0.35s ease-out backwards;
  box-shadow: inset 0 0 24px rgba(0, 240, 255, 0.04);
}

.step-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}
.step-num {
  font-family: "Orbitron", monospace;
  font-size: 11px;
  letter-spacing: 3px;
  color: var(--cyan);
  text-shadow: 0 0 6px var(--cyan);
}
.step-annotation {
  font-family: "IBM Plex Sans", sans-serif;
  font-size: 12px;
  color: var(--muted);
  font-style: italic;
}

.step-expr {
  font-family: "JetBrains Mono", monospace;
  font-size: 17px;
  color: var(--text);
  letter-spacing: 1px;
  margin: 6px 0;
}
.step-expr .highlight {
  color: var(--pink);
  text-shadow: var(--glow-pink);
  padding: 1px 4px;
  border-radius: 2px;
  background: rgba(255, 45, 106, 0.08);
}

.step-result {
  font-family: "JetBrains Mono", monospace;
  font-size: 14px;
  color: var(--mint);
  text-shadow: 0 0 6px rgba(57, 255, 20, 0.6);
  margin-top: 4px;
}
.step-arrow { color: var(--muted); margin: 0 6px; }

/* Answer */
.answer-section { min-height: 10px; }
.answer-box {
  text-align: center;
  padding: 30px 20px;
  background: var(--surface);
  border: 1px solid var(--mint);
  border-radius: 4px;
  box-shadow: var(--glow-mint), inset 0 0 30px rgba(57, 255, 20, 0.05);
  animation: pulse-glow 2.5s ease-in-out infinite;
}
.answer-label {
  font-family: "Orbitron", monospace;
  font-size: 11px;
  letter-spacing: 4px;
  color: var(--mint);
  text-shadow: var(--glow-mint);
  margin-bottom: 16px;
}
.answer-value {
  display: block;
  text-align: center;
  font-family: "JetBrains Mono", monospace;
  font-size: 56px;
  font-weight: 700;
  color: var(--mint);
  text-shadow: var(--glow-mint);
  letter-spacing: 2px;
}
.answer-actions {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-top: 16px;
}
.answer-actions .share-btn {
  padding: 8px 14px;
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
  letter-spacing: 2px;
  border-radius: 3px;
}
.copy-btn {
  background: transparent;
  border: 1px solid var(--mint);
  color: var(--mint);
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
  letter-spacing: 2px;
  padding: 8px 14px;
  cursor: pointer;
  border-radius: 3px;
  text-shadow: 0 0 4px var(--mint);
  transition: transform 0.15s;
}
.copy-btn:hover { transform: scale(1.05); box-shadow: var(--glow-mint); }

/* History */
.history-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}

.history-list {
  list-style: none;
  background: var(--surface);
  border: 1px solid var(--grid);
  border-radius: 4px;
  overflow: hidden;
}
.history-list li {
  padding: 10px 16px;
  font-family: "JetBrains Mono", monospace;
  font-size: 13px;
  border-bottom: 1px solid var(--grid);
  cursor: pointer;
  color: var(--text);
  transition: background 0.15s, color 0.15s;
  display: flex;
  justify-content: space-between;
  gap: 12px;
}
.history-list li:last-child { border-bottom: none; }
.history-list li:hover {
  background: rgba(0, 240, 255, 0.05);
  color: var(--cyan);
  border-left: 3px solid var(--pink);
  padding-left: 13px;
}
.history-list .hist-expr { color: var(--text); }
.history-list .hist-eq { color: var(--muted); margin: 0 6px; }
.history-list .hist-answer { color: var(--mint); text-shadow: 0 0 4px var(--mint); }

.placeholder {
  font-family: "JetBrains Mono", monospace;
  color: var(--muted);
  font-size: 12px;
  letter-spacing: 1px;
  font-style: italic;
  padding: 6px;
}

/* Toast */
.toast {
  position: fixed;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--surface);
  border: 1px solid var(--mint);
  color: var(--mint);
  padding: 12px 24px;
  border-radius: 3px;
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
  letter-spacing: 2px;
  text-shadow: 0 0 6px var(--mint);
  box-shadow: var(--glow-mint);
  opacity: 0;
  transition: opacity 0.3s, transform 0.3s;
  z-index: 9998;
  pointer-events: none;
}
.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

.hidden { display: none !important; }

/* Animations */
@keyframes pop-in {
  from { opacity: 0; transform: scale(0.7); }
  to { opacity: 1; transform: scale(1); }
}
@keyframes slide-in {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-6px); }
  40% { transform: translateX(6px); }
  60% { transform: translateX(-4px); }
  80% { transform: translateX(4px); }
}
@keyframes pulse-glow {
  0%, 100% { box-shadow: var(--glow-mint), inset 0 0 30px rgba(57, 255, 20, 0.05); }
  50% { box-shadow: 0 0 10px #39ff14, 0 0 30px rgba(57, 255, 20, 0.8), 0 0 60px rgba(57, 255, 20, 0.4), inset 0 0 40px rgba(57, 255, 20, 0.1); }
}

@media (max-width: 640px) {
  .container { padding: 20px 14px; }
  #expr { font-size: 18px; }
  .answer-value { font-size: 40px; }
  .logo { font-size: 14px; letter-spacing: 2px; }
  .logo-sub { display: none; }
}

.app-footer {
  text-align: center;
  padding: 24px 16px 40px;
  color: var(--muted, #606090);
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  letter-spacing: 2px;
  text-transform: uppercase;
  opacity: 0.7;
  pointer-events: none;
}
.app-footer .footer-line {
  margin: 0 10px;
  opacity: 0.4;
}
@media (max-width: 480px) {
  .app-footer { padding-bottom: 24px; }
}