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

:root {
  --bg:       #090918;
  --panel-bg: rgba(8, 10, 28, 0.88);
  --accent:   #00ccff;
  --accent2:  #a855f7;
  --text:     #ccd6f6;
  --muted:    #8892b0;
  --border:   rgba(0, 204, 255, 0.18);
  --glow:     0 0 16px rgba(0, 204, 255, 0.25);
  --radius:   8px;
  --font:     'Inter', 'Segoe UI', system-ui, sans-serif;
}

html, body {
  width: 100%; height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 13px;
  overflow: hidden;
}

/* ── Layout ─────────────────────────────────── */
#app {
  display: flex;
  width: 100vw;
  height: 100vh;
  position: relative;
}

#canvas {
  flex: 1;
  display: block;
  min-width: 0;
  background: var(--bg);
  cursor: grab;
}
#canvas:active { cursor: grabbing; }

#axes-canvas {
  position: absolute;
  top: 0; left: 0;
  pointer-events: none;
  z-index: 5;
}

/* ── Side panel ─────────────────────────────── */
#panel {
  width: 260px;
  flex-shrink: 0;
  background: var(--panel-bg);
  border-left: 1px solid var(--border);
  backdrop-filter: blur(18px);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  gap: 0;
}

.panel-title {
  padding: 18px 16px 12px;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  text-shadow: var(--glow);
  border-bottom: 1px solid var(--border);
}

.panel-section {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.section-label {
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: -2px;
}
/* ── Dual-handle slit slider ────────────────────── */
.dual-range {
  position: relative;
  height: 18px;
  margin: 2px 0;
}
.dual-track {
  position: absolute;
  top: 7px;
  left: 0; right: 0;
  height: 4px;
  border-radius: 2px;
  background: rgba(0,204,255,0.15);
  pointer-events: none;
}
.dual-range input[type="range"] {
  position: absolute;
  width: 100%;
  height: 4px;
  top: 7px;
  margin: 0;
  padding: 0;
  pointer-events: none;
  background: transparent;
  appearance: none;
  -webkit-appearance: none;
  outline: none;
}
.dual-range input[type="range"]::-webkit-slider-thumb {
  pointer-events: all;
  -webkit-appearance: none;
  width: 14px; height: 14px;
  border-radius: 50%;
  cursor: pointer;
  transition: transform .1s;
}
.dual-range input[type="range"]::-webkit-slider-thumb:hover { transform: scale(1.25); }
.dual-range input[type="range"]::-moz-range-thumb {
  pointer-events: all;
  width: 14px; height: 14px;
  border: none;
  border-radius: 50%;
  cursor: pointer;
}
#slit1::-webkit-slider-thumb { background: #00ccff; box-shadow: 0 0 8px #00ccff; }
#slit1::-moz-range-thumb      { background: #00ccff; box-shadow: 0 0 8px #00ccff; }
#slit2::-webkit-slider-thumb { background: #ff6b6b; box-shadow: 0 0 8px #ff6b6b; }
#slit2::-moz-range-thumb      { background: #ff6b6b; box-shadow: 0 0 8px #ff6b6b; }
/* ── Sliders ─────────────────────────────────── */
.slider-row {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.slider-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.slider-name {
  font-size: 12px;
  color: var(--text);
}

.slider-val {
  font-size: 11px;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  min-width: 62px;
  text-align: right;
}

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  border-radius: 2px;
  background: rgba(0, 204, 255, 0.15);
  outline: none;
  cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 14px; height: 14px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent);
  cursor: pointer;
  transition: transform 0.1s;
}
input[type="range"]::-webkit-slider-thumb:hover { transform: scale(1.25); }
input[type="range"]::-moz-range-thumb {
  width: 14px; height: 14px;
  border: none;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent);
  cursor: pointer;
}

/* ── Panel tabs ─────────────────────────────── */
.panel-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}
button.tab-btn {
  flex: 1;
  padding: 7px 0;
  border: none;
  border-radius: 0;
  border-bottom: 2px solid transparent;
  background: transparent;
  color: var(--muted);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
  transition: color .15s;
  box-shadow: none;
}
button.tab-btn:hover {
  background: transparent;
  box-shadow: none;
  border-color: transparent;
  color: var(--text);
}
button.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}
/* Show/hide basic vs expert panel sections */
.panel-section[data-tab="expert"] { display: none; }
#panel.show-expert .panel-section[data-tab="expert"] { display: flex; }
#panel.show-expert .panel-section[data-tab="basic"] { display: none; }

/* ── Panel tabs ─────────────────────────────── */
.panel-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}
button.tab-btn {
  flex: 1;
  padding: 7px 0;
  border: none;
  border-radius: 0;
  border-bottom: 2px solid transparent;
  background: transparent;
  color: var(--muted);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
  transition: color .15s;
  box-shadow: none;
}
button.tab-btn:hover {
  background: transparent;
  box-shadow: none;
  border-color: transparent;
  color: var(--text);
}
button.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}
/* Show/hide basic vs expert panel sections */
.panel-section[data-tab="expert"] { display: none; }
#panel.show-expert .panel-section[data-tab="expert"] { display: flex; }
#panel.show-expert .panel-section[data-tab="basic"] { display: none; }

/* ── Buttons ─────────────────────────────────── */
.btn-row {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

button {
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: rgba(0, 204, 255, 0.07);
  color: var(--text);
  font-family: var(--font);
  font-size: 12px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, box-shadow 0.15s, border-color 0.15s;
  letter-spacing: 0.03em;
}
button:hover {
  background: rgba(0, 204, 255, 0.18);
  box-shadow: var(--glow);
  border-color: var(--accent);
  color: #fff;
}
/* Inline pair of buttons */
.btn-row-inline {
  display: flex;
  gap: 6px;
}
.btn-row-inline button {
  flex: 1;
  font-size: 11px;
  padding: 6px 6px;
}
.btn-toggle.btn-off {
  opacity: 0.38;
  border-color: var(--border);
  background: transparent;
  color: var(--muted);
}
.btn-toggle.btn-off:hover {
  opacity: 0.7;
  background: rgba(0, 204, 255, 0.08);
  box-shadow: none;
}

button#btn-reset {
  border-color: rgba(168, 85, 247, 0.5);
  background: rgba(168, 85, 247, 0.10);
}
button#btn-reset:hover {
  background: rgba(168, 85, 247, 0.25);
  box-shadow: 0 0 16px rgba(168, 85, 247, 0.3);
  border-color: var(--accent2);
}

/* Start / Stop button */
button#btn-pause {
  font-size: 12px;
  font-weight: 700;
  padding: 6px 10px;
  letter-spacing: 0.04em;
}
button#btn-pause.btn-running {
  border-color: rgba(0, 255, 128, 0.55);
  background: rgba(0, 255, 128, 0.10);
  color: #00ff88;
}
button#btn-pause.btn-running:hover {
  background: rgba(0, 255, 128, 0.22);
  box-shadow: 0 0 18px rgba(0, 255, 128, 0.35);
  border-color: #00ff88;
}

/* Resolution / select */
select {
  width: 100%;
  padding: 7px 28px 7px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: rgba(0, 204, 255, 0.07);
  color: var(--text);
  font-family: var(--font);
  font-size: 12px;
  cursor: pointer;
  outline: none;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M0 0l5 6 5-6z' fill='%2300ccff'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
}
select:hover, select:focus {
  border-color: var(--accent);
  box-shadow: var(--glow);
}
select option {
  background: #0d1228;
  color: var(--text);
}
/* ── Palette picker ─────────────────────────── */
.appearance-row {
  display: flex;
  gap: 8px;
}
.appearance-col {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.appearance-label {
  font-size: 10px;
  color: var(--muted);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.palette-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 5px 9px;
  background: rgba(0,204,255,0.05);
  transition: border-color .2s, box-shadow .2s;
  user-select: none;
}
/* Compact variant — strip fills all available space, no text label */
.palette-btn-compact {
  padding: 5px 7px;
  gap: 5px;
}
.palette-btn:hover {
  border-color: var(--accent);
  box-shadow: var(--glow);
}
.palette-strip-cur {
  flex: 1;
  height: 16px;
  border-radius: 4px;
}
.palette-label-cur {
  font-size: 11px;
  color: var(--muted);
  white-space: nowrap;
  min-width: 52px;
  text-align: right;
}
.palette-arrow {
  font-size: 11px;
  color: var(--accent);
  line-height: 1;
}
.palette-popup {
  position: fixed;
  z-index: 9999;
  background: rgba(8, 10, 28, 0.97);
  border: 1px solid rgba(0,204,255,0.30);
  border-radius: 10px;
  padding: 7px;
  box-shadow: 0 12px 44px rgba(0,0,0,0.80);
  width: 240px;
  display: none;
  backdrop-filter: blur(16px);
}
.palette-option {
  display: flex;
  align-items: center;
  gap: 9px;
  cursor: pointer;
  border-radius: 6px;
  padding: 5px 7px;
  border: 2px solid transparent;
  transition: background .15s;
}
.palette-option:hover  { background: rgba(0,204,255,0.10); }
.palette-option.active { border-color: var(--accent); }
.palette-option .p-strip {
  flex: 1;
  height: 14px;
  border-radius: 3px;
}
.palette-option .p-name {
  width: 66px;
  font-size: 11px;
  color: var(--muted);
  text-align: right;
  white-space: nowrap;
}

.particle-dot-cur {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  flex-shrink: 0;
  border: 2px solid rgba(255,255,255,0.25);
}

/* Particle colour popup — floating dot grid */
.particle-popup {
  position: fixed;
  z-index: 9999;
  background: rgba(8, 10, 28, 0.97);
  border: 1px solid rgba(0,204,255,0.30);
  border-radius: 10px;
  padding: 10px;
  box-shadow: 0 12px 44px rgba(0,0,0,0.80);
  display: none;
  flex-wrap: wrap;
  gap: 8px;
  width: 200px;
  backdrop-filter: blur(16px);
}
.particle-popup .p-dot {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  cursor: pointer;
  border: 2px solid rgba(255,255,255,0.12);
  transition: transform .15s, border-color .15s, box-shadow .15s;
}
.particle-popup .p-dot:hover  { transform: scale(1.2); border-color: rgba(255,255,255,0.45); }
.particle-popup .p-dot.active { border-color: #fff; box-shadow: 0 0 10px rgba(255,255,255,0.55); }

/* ── HUD overlay ─────────────────────────────── */
#hud {
  position: absolute;
  top: 14px;
  left: 14px;
  pointer-events: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.hud-item {
  background: rgba(9, 9, 24, 0.72);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: 4px 10px;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
  color: var(--accent);
  backdrop-filter: blur(6px);
  letter-spacing: 0.05em;
}

/* ── Scrollbar ───────────────────────────────── */
#panel::-webkit-scrollbar { width: 4px; }
#panel::-webkit-scrollbar-track { background: transparent; }
#panel::-webkit-scrollbar-thumb { background: rgba(0,204,255,0.2); border-radius: 2px; }

/* ── Responsive: stack on narrow screens ─────── */
@media (max-width: 620px) {
  #app { flex-direction: column; }
  #panel { width: 100%; height: 220px; flex-shrink: 0; border-left: none; border-top: 1px solid var(--border); flex-direction: row; overflow-x: auto; overflow-y: hidden; flex-wrap: nowrap; }
  .panel-title { display: none; }
  .panel-section { border-bottom: none; border-right: 1px solid var(--border); min-width: 200px; }
}