/* ===== DESIGN TOKENS ===== */
:root {
  --color-bg:          #0f1117;
  --color-surface:     #1a1d27;
  --color-surface-2:   #23263a;
  --color-border:      #2e3148;
  --color-text:        #e8eaf6;
  --color-text-muted:  #7b7f9e;
  --color-accent-dl:   #4f9eff;
  --color-accent-ul:   #a78bfa;
  --color-error:       #f87171;
  --color-accent:      var(--color-accent-dl);

  --space-xs:  4px;
  --space-sm:  8px;
  --space-md:  16px;
  --space-lg:  24px;
  --space-xl:  40px;

  --font-family: 'Inter', system-ui, -apple-system, sans-serif;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --progress-height: 22px;
  --progress-pct:    0%;
}

/* ===== RESET & BASE ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-family);
  font-size: 15px;
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: var(--space-xl) var(--space-md);
}

/* ===== APP SHELL ===== */
.app {
  width: 100%;
  max-width: 740px;
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

/* ===== CARD ===== */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.divider {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 0;
}

/* ===== HEADER ===== */
header {
  text-align: center;
}

h1 {
  font-size: clamp(22px, 5vw, 32px);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--color-text);
}

.subtitle {
  margin-top: var(--space-xs);
  color: var(--color-text-muted);
  font-size: 14px;
}

/* ===== CONFIG PANEL ===== */
.config-panel {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: var(--space-md);
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  min-width: 0;
}

.input-group label {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.input-row {
  display: flex;
  gap: var(--space-xs);
}

.input-row input[type="number"] {
  flex: 1;
  min-width: 0;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-family: inherit;
  font-size: 15px;
  padding: var(--space-sm) var(--space-sm);
  outline: none;
  transition: border-color 0.15s;
  -moz-appearance: textfield;
}

.input-row input[type="number"]::-webkit-outer-spin-button,
.input-row input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
}

.input-row input[type="number"]:focus {
  border-color: var(--color-accent);
}

.input-row select {
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-family: inherit;
  font-size: 13px;
  padding: var(--space-sm) var(--space-xs);
  outline: none;
  cursor: pointer;
  flex-shrink: 0;
  width: 68px;
  transition: border-color 0.15s;
}

.input-row select:focus {
  border-color: var(--color-accent);
}

/* Error state */
.input-group .error-msg {
  display: none;
  font-size: 12px;
  color: var(--color-error);
}

.input-group.error .error-msg {
  display: block;
}

.input-group.error input,
.input-group.error select {
  border-color: var(--color-error);
}

/* ===== PRESETS ===== */
.presets-panel {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.presets-label {
  font-size: 12px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
}

.preset-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-sm);
}

.preset-btn {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-family: inherit;
  font-size: 13px;
  font-weight: 500;
  padding: var(--space-xs) var(--space-md);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, color 0.15s;
  text-align: center;
}

.preset-btn span {
  color: var(--color-text-muted);
  font-weight: 400;
  margin-left: 4px;
}

.preset-btn:hover {
  border-color: var(--color-accent-dl);
  background: var(--color-surface-2);
}

.preset-btn.active {
  border-color: var(--color-accent-dl);
  background: color-mix(in srgb, var(--color-accent-dl) 12%, var(--color-surface));
  color: var(--color-accent-dl);
}

.preset-btn.active span {
  color: color-mix(in srgb, var(--color-accent-dl) 70%, var(--color-text-muted));
}

/* ===== ACTION BUTTONS ===== */
.action-panel {
  display: flex;
  gap: var(--space-md);
}

.action-btn {
  flex: 1;
  padding: 14px var(--space-md);
  border: none;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.15s, transform 0.1s;
  letter-spacing: 0.01em;
}

.action-btn:active {
  transform: scale(0.98);
}

.action-btn:disabled {
  opacity: 0.35;
  pointer-events: none;
  cursor: default;
}

.download-btn {
  background: var(--color-accent-dl);
  color: #fff;
}

.upload-btn {
  background: var(--color-accent-ul);
  color: #fff;
}

/* ===== PROGRESS PANEL ===== */
.progress-panel {
  display: none;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-lg) var(--space-lg) var(--space-md);
  gap: var(--space-lg);
  flex-direction: column;
}

.progress-panel.visible {
  display: flex;
}

.transfer-label {
  font-size: 17px;
  font-weight: 600;
  color: var(--color-accent);
}

/* Progress bar */
.progress-track {
  background: var(--color-surface-2);
  border-radius: 999px;
  height: var(--progress-height);
  overflow: hidden;
  position: relative;
}

.progress-bar {
  height: 100%;
  width: var(--progress-pct);
  background: var(--color-accent);
  border-radius: 999px;
  position: relative;
  overflow: hidden;
  transition: none;
  min-width: 0;
}

.progress-glow {
  position: absolute;
  inset: 0;
  background: linear-gradient(
    90deg,
    transparent 0%,
    rgba(255, 255, 255, 0.22) 50%,
    transparent 100%
  );
  animation: shimmer 1.8s linear infinite;
}

@keyframes shimmer {
  from { transform: translateX(-100%); }
  to   { transform: translateX(100%); }
}

/* Stats */
.stats-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-sm);
  text-align: center;
}

.stat-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  background: var(--color-surface-2);
  border-radius: var(--radius-sm);
  padding: var(--space-sm) var(--space-xs);
}

.stat-value {
  font-size: 17px;
  font-weight: 700;
  color: var(--color-text);
  font-variant-numeric: tabular-nums;
}

.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
}

/* Cancel button */
.cancel-btn {
  align-self: center;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  font-family: inherit;
  font-size: 13px;
  padding: var(--space-xs) var(--space-lg);
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
}

.cancel-btn:hover {
  border-color: var(--color-error);
  color: var(--color-error);
}

/* ===== FOOTER ===== */
footer {
  text-align: center;
}

footer p {
  font-size: 12px;
  color: var(--color-text-muted);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 540px) {
  .card {
    padding: var(--space-md);
    border-radius: var(--radius-md);
  }

  .config-panel {
    grid-template-columns: 1fr;
  }

  .preset-buttons {
    grid-template-columns: repeat(2, 1fr);
  }

  .stats-row {
    grid-template-columns: repeat(2, 1fr);
  }
}