:root {
  --brand: #1a73e8;
  --brand-dark: #1557b0;
  --green: #188038;
  --green-light: #e6f4ea;
  --ink: #202124;
  --ink-soft: #5f6368;
  --line: #dadce0;
  --bg: #ffffff;
  --bg-soft: #f8f9fa;
  --radius: 12px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

.wrap { max-width: 940px; margin: 0 auto; padding: 0 20px; }

/* ---------- header ---------- */
.site-header {
  border-bottom: 1px solid var(--line);
  background: #fff;
  position: sticky;
  top: 0;
  z-index: 50;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  padding-bottom: 14px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  color: var(--ink);
  font-size: 19px;
  font-weight: 600;
  letter-spacing: -0.2px;
}
.logo-mark { font-size: 22px; }
.logo-thin { font-weight: 400; color: var(--ink-soft); }

.privacy-badge {
  background: var(--green-light);
  color: var(--green);
  font-size: 12.5px;
  font-weight: 600;
  padding: 6px 12px;
  border-radius: 999px;
  white-space: nowrap;
}

/* ---------- hero ---------- */
.hero {
  padding: 56px 0 40px;
  text-align: center;
  background: linear-gradient(180deg, #f8fbff 0%, #ffffff 100%);
  border-bottom: 1px solid var(--line);
}
.hero h1 {
  font-size: 40px;
  line-height: 1.22;
  font-weight: 700;
  letter-spacing: -0.8px;
  margin-bottom: 18px;
}
.hero h1 .hl { color: var(--brand); }
.hero-sub {
  font-size: 17px;
  color: var(--ink-soft);
  max-width: 680px;
  margin: 0 auto;
}
.hero-sub strong { color: var(--ink); font-weight: 600; }

.trust-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px 22px;
  margin-top: 26px;
}
.trust-item {
  font-size: 14px;
  color: var(--green);
  font-weight: 500;
}

/* ---------- tool ---------- */
.tool-section { padding: 48px 0 40px; }

.tool-card {
  border: 1px solid var(--line);
  border-radius: 16px;
  background: #fff;
  overflow: hidden;
  box-shadow: 0 1px 3px rgba(0,0,0,.04);
}

.tabs {
  display: flex;
  border-bottom: 1px solid var(--line);
  background: var(--bg-soft);
}
.tab {
  flex: 1;
  padding: 15px 10px;
  border: none;
  background: transparent;
  font-size: 15px;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
  border-bottom: 3px solid transparent;
  transition: all .15s;
}
.tab:hover { color: var(--ink); background: #f1f3f4; }
.tab.active {
  color: var(--brand);
  border-bottom-color: var(--brand);
  background: #fff;
}

.panel { display: none; padding: 26px 24px 28px; }
.panel.active { display: block; }
.panel-desc {
  color: var(--ink-soft);
  font-size: 15px;
  margin-bottom: 18px;
}

/* dropzone */
.dropzone {
  border: 2px dashed var(--line);
  border-radius: var(--radius);
  padding: 40px 20px;
  text-align: center;
  cursor: pointer;
  transition: all .15s;
  background: #fcfcfd;
}
.dropzone:hover, .dropzone.dragover {
  border-color: var(--brand);
  background: #f4f8ff;
}
.dz-icon {
  font-size: 30px;
  color: var(--brand);
  margin-bottom: 10px;
}
.dz-main { font-size: 16px; font-weight: 600; margin-bottom: 4px; }
.dz-sub { font-size: 14px; color: var(--ink-soft); }
.dz-link { color: var(--brand); font-weight: 500; text-decoration: underline; }

/* file list */
.file-list {
  list-style: none;
  margin-top: 18px;
}
.file-list:empty { display: none; }
.file-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 11px 14px;
  border: 1px solid var(--line);
  border-radius: 9px;
  margin-bottom: 8px;
  background: #fff;
}
.file-item .fidx {
  width: 24px;
  height: 24px;
  flex-shrink: 0;
  border-radius: 50%;
  background: var(--bg-soft);
  color: var(--ink-soft);
  font-size: 12px;
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
}
.file-item .fname {
  flex: 1;
  font-size: 14px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.file-item .fsize {
  font-size: 12.5px;
  color: var(--ink-soft);
  flex-shrink: 0;
}
.file-item .fbtns { display: flex; gap: 4px; flex-shrink: 0; }
.file-item .fbtn {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink-soft);
  width: 26px;
  height: 26px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 12px;
  line-height: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}
.file-item .fbtn:hover { background: var(--bg-soft); color: var(--ink); }
.file-item .fbtn.del:hover { color: #d93025; border-color: #f5c6c4; }

/* split options */
.split-options {
  margin-top: 18px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--bg-soft);
}
.file-meta {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 14px;
  color: var(--green);
}
.field { display: block; margin-bottom: 14px; flex: 1; }
.field > span {
  display: block;
  font-size: 13px;
  font-weight: 500;
  color: var(--ink-soft);
  margin-bottom: 5px;
}
.field input, .field select {
  width: 100%;
  padding: 9px 11px;
  border: 1px solid var(--line);
  border-radius: 8px;
  font-size: 14px;
  font-family: inherit;
  background: #fff;
}
.field input:focus, .field select:focus {
  outline: none;
  border-color: var(--brand);
}
.field-row { display: flex; gap: 14px; }

/* actions */
.actions {
  display: flex;
  gap: 10px;
  margin-top: 20px;
}
.btn {
  padding: 12px 26px;
  border-radius: 9px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid transparent;
  font-family: inherit;
  transition: all .15s;
}
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--brand-dark); }
.btn-primary:disabled { background: #c5c9cd; cursor: not-allowed; }
.btn-ghost {
  background: #fff;
  color: var(--ink-soft);
  border-color: var(--line);
}
.btn-ghost:hover { background: var(--bg-soft); }

.status {
  margin-top: 14px;
  font-size: 14px;
  min-height: 22px;
  color: var(--green);
  font-weight: 500;
}
.status.error { color: #d93025; }

.reassure {
  text-align: center;
  font-size: 13.5px;
  color: var(--ink-soft);
  margin-top: 20px;
}

/* ---------- why ---------- */
.why {
  padding: 56px 0;
  background: var(--bg-soft);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.why h2, .howto h2, .faq h2 {
  font-size: 27px;
  font-weight: 700;
  margin-bottom: 30px;
  letter-spacing: -0.4px;
}
.why-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 20px;
}
.why-item {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
}
.why-icon { font-size: 26px; margin-bottom: 12px; }
.why-item h3 { font-size: 16.5px; margin-bottom: 9px; font-weight: 600; }
.why-item p { font-size: 14.5px; color: var(--ink-soft); }

/* ---------- howto ---------- */
.howto { padding: 56px 0; }
.steps { padding-left: 22px; max-width: 720px; }
.steps li {
  margin-bottom: 13px;
  font-size: 15.5px;
  color: var(--ink-soft);
}
.steps li strong { color: var(--ink); }
.howto-note {
  margin-top: 16px;
  font-size: 14.5px;
  color: var(--ink-soft);
  font-style: italic;
}

/* ---------- faq ---------- */
.faq {
  padding: 56px 0;
  background: var(--bg-soft);
  border-top: 1px solid var(--line);
}
.faq-item {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  margin-bottom: 11px;
  overflow: hidden;
}
.faq-item summary {
  padding: 16px 20px;
  font-size: 15.5px;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  font-size: 21px;
  color: var(--ink-soft);
  font-weight: 400;
  flex-shrink: 0;
}
.faq-item[open] summary::after { content: "−"; }
.faq-item summary:hover { background: #fafbfc; }
.faq-item p {
  padding: 0 20px 18px;
  font-size: 14.5px;
  color: var(--ink-soft);
}

/* ---------- footer ---------- */
.site-footer {
  padding: 34px 0;
  text-align: center;
  border-top: 1px solid var(--line);
}
.footer-main { font-size: 14.5px; font-weight: 600; margin-bottom: 5px; }
.footer-sub { font-size: 13px; color: var(--ink-soft); }

/* ---------- responsive ---------- */
@media (max-width: 640px) {
  .hero h1 { font-size: 29px; }
  .hero-sub { font-size: 15.5px; }
  .why h2, .howto h2, .faq h2 { font-size: 23px; }
  .panel { padding: 20px 16px 24px; }
  .field-row { flex-direction: column; gap: 0; }
  .privacy-badge { font-size: 11.5px; padding: 5px 10px; }
  .actions { flex-direction: column; }
  .btn { width: 100%; }
}