/* ─── CSS variables (light theme default) ──────────────────────────────── */
:root {
  --bg: #f0f2f5;
  --card-bg: #ffffff;
  --card-shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
  --text: #1a1a2e;
  --muted: #718096;
  --border: #e2e8f0;
  --surface: #f7fafc;
  --drop-border: #a0aec0;
  --drop-hover-bg: #ebf4ff;
  --drop-hover-border: #4299e1;
  --drop-hover-text: #2b6cb0;
  --accent: #4299e1;
  --accent-hover: #3182ce;
  --receiver-bg: #f0fff4;
  --receiver-border: #9ae6b4;
  --receiver-text: #276749;
  --receiver-label: #48bb78;
  --progress-track: #e2e8f0;
  --progress-fill: #4299e1;
  --download-bg: #48bb78;
  --download-hover: #38a169;
  --error: #e53e3e;
}

/* ─── Dark theme ────────────────────────────────────────────────────────── */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1117;
    --card-bg: #1a1d27;
    --card-shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
    --text: #e2e8f0;
    --muted: #718096;
    --border: #2d3748;
    --surface: #252836;
    --drop-border: #4a5568;
    --drop-hover-bg: #1a2744;
    --drop-hover-border: #4299e1;
    --drop-hover-text: #90cdf4;
    --accent: #4299e1;
    --accent-hover: #63b3ed;
    --receiver-bg: #0d2b1f;
    --receiver-border: #2f855a;
    --receiver-text: #68d391;
    --receiver-label: #48bb78;
    --progress-track: #2d3748;
    --progress-fill: #63b3ed;
    --download-bg: #2f855a;
    --download-hover: #38a169;
    --error: #fc8181;
  }
}

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

[hidden] { display: none !important; }

body {
  font-family: system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 1rem;
}

/* ─── Card ──────────────────────────────────────────────────────────────── */
.card {
  background: var(--card-bg);
  border-radius: 14px;
  padding: 2rem;
  width: 100%;
  max-width: 480px;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

h1 {
  font-size: 1.4rem;
  color: var(--text);
}

/* ─── Drop zone ─────────────────────────────────────────────────────────── */
#drop-zone {
  border: 2px dashed var(--drop-border);
  border-radius: 10px;
  padding: 2.5rem 1rem;
  text-align: center;
  cursor: pointer;
  color: var(--muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
  user-select: none;
}

#drop-zone p {
  font-size: 1rem;
  font-weight: 500;
}

#drop-zone span {
  font-size: 0.8rem;
}

#drop-zone:hover,
#drop-zone.dragover {
  background: var(--drop-hover-bg);
  border-color: var(--drop-hover-border);
  color: var(--drop-hover-text);
}

#drop-zone input[type="file"] { display: none; }

/* ─── Receiver view ─────────────────────────────────────────────────────── */
#receiver-view {
  background: var(--receiver-bg);
  border: 1.5px solid var(--receiver-border);
  border-radius: 10px;
  padding: 1.5rem 1.25rem;
}

.receiver-badge {
  display: flex;
  align-items: center;
  gap: 1rem;
  color: var(--receiver-text);
}

.receiver-label {
  font-size: 0.75rem;
  color: var(--receiver-label);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.2rem;
}

.receiver-room-id {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: 0.12em;
}

/* ─── File info ─────────────────────────────────────────────────────────── */
#file-info {
  background: var(--surface);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.info-row {
  display: flex;
  gap: 0.75rem;
  font-size: 0.9rem;
}

.info-label {
  color: var(--muted);
  min-width: 36px;
}

.info-row span:last-child {
  font-weight: 600;
  color: var(--text);
  word-break: break-all;
}

/* ─── Password section (sender) + join form (receiver) ─────────────────── */
#password-section {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

#password-section label {
  font-size: 0.82rem;
  color: var(--muted);
}

.optional {
  font-size: 0.75rem;
  opacity: 0.7;
}

.input-row,
.join-form {
  display: flex;
  gap: 0.5rem;
}

.join-form {
  margin-top: 1rem;
}

.input-row input[type="password"],
.join-form input[type="password"] {
  flex: 1;
  min-width: 0;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.85rem;
  color: var(--text);
  background: var(--surface);
  outline: none;
}

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

#create-btn,
#join-btn {
  padding: 0.5rem 1rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
  white-space: nowrap;
  transition: background 0.15s;
}

#create-btn:hover,
#join-btn:hover { background: var(--accent-hover); }

#create-btn:disabled,
#join-btn:disabled { opacity: 0.6; cursor: not-allowed; }

/* ─── Link section ──────────────────────────────────────────────────────── */
#link-section {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

#link-section label {
  font-size: 0.82rem;
  color: var(--muted);
}

.link-row {
  display: flex;
  gap: 0.5rem;
}

#share-link {
  flex: 1;
  min-width: 0;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.82rem;
  color: var(--text);
  background: var(--surface);
  outline: none;
}

#copy-btn {
  padding: 0.5rem 1rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
  white-space: nowrap;
  transition: background 0.15s;
}

#copy-btn:hover { background: var(--accent-hover); }

/* ─── QR code ───────────────────────────────────────────────────────────── */
#qr-code {
  display: flex;
  justify-content: center;
  padding-top: 0.25rem;
}

#qr-code canvas,
#qr-code img {
  border-radius: 6px;
}

/* ─── Transfer progress ─────────────────────────────────────────────────── */
#transfer-section {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.progress-wrap {
  height: 8px;
  background: var(--progress-track);
  border-radius: 99px;
  overflow: hidden;
}

#progress-bar {
  height: 100%;
  width: 0%;
  background: var(--progress-fill);
  border-radius: 99px;
  transition: width 0.12s ease-out;
}

.progress-stats {
  display: flex;
  justify-content: space-between;
  font-size: 0.82rem;
  color: var(--muted);
}

/* ─── Download button ───────────────────────────────────────────────────── */
#download-section {
  display: flex;
  justify-content: center;
}

#download-btn {
  display: inline-block;
  padding: 0.75rem 2.5rem;
  background: var(--download-bg);
  color: #fff;
  border-radius: 8px;
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 600;
  transition: background 0.15s;
}

#download-btn:hover { background: var(--download-hover); }

/* ─── Status ────────────────────────────────────────────────────────────── */
#status {
  font-size: 0.88rem;
  color: var(--muted);
  min-height: 1.2em;
}

#status.error { color: var(--error); }

/* ─── Responsive (mobile) ───────────────────────────────────────────────── */
@media (max-width: 480px) {
  body { padding: 0; align-items: flex-start; }

  .card {
    border-radius: 0;
    box-shadow: none;
    min-height: 100svh;
    padding: 1.5rem 1.25rem;
  }
}