:root {
  color-scheme: light;
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-strong: #eef3f6;
  --ink: #151923;
  --muted: #5f6b78;
  --line: #d8e1ea;
  --accent: #007f73;
  --accent-soft: #dff4ef;
  --coral: #d86f45;
  --shadow: 0 18px 50px rgba(17, 24, 39, 0.1);
  --radius: 8px;
  --max-width: 1220px;
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg: #111419;
  --surface: #1a1f27;
  --surface-strong: #232a35;
  --ink: #f5f7fb;
  --muted: #b5bfcb;
  --line: #323b48;
  --accent: #45c7b5;
  --accent-soft: #143a36;
  --coral: #ff9b70;
  --shadow: 0 20px 60px rgba(0, 0, 0, 0.28);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-width: 320px;
  background:
    linear-gradient(90deg, rgba(0, 127, 115, 0.07), transparent 34%),
    linear-gradient(180deg, rgba(216, 111, 69, 0.07), transparent 36%),
    var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.55;
}

a {
  color: inherit;
}

button,
input,
select {
  font: inherit;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem max(1rem, calc((100vw - var(--max-width)) / 2));
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface), transparent 8%);
  backdrop-filter: blur(16px);
}

.brand,
.app-header nav {
  display: flex;
  align-items: center;
  gap: 0.7rem;
}

.brand,
.app-header a {
  text-decoration: none;
}

.brand span {
  display: grid;
  width: 42px;
  height: 42px;
  place-items: center;
  border-radius: var(--radius);
  background: var(--ink);
  color: var(--surface);
  font-weight: 900;
}

.app-header nav a,
.theme-toggle,
.panel-heading button,
.file-actions button,
.primary-action,
.download-action {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-weight: 800;
  min-height: 38px;
  padding: 0.55rem 0.75rem;
  text-decoration: none;
}

.app-shell {
  width: min(var(--max-width), calc(100% - 2rem));
  margin: 0 auto;
  padding: 4rem 0 5rem;
}

.intro {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 220px;
  gap: 1rem;
  align-items: end;
  margin-bottom: 1.4rem;
}

.intro > div:first-child {
  max-width: 820px;
}

.eyebrow {
  margin: 0 0 0.7rem;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 1rem;
  font-size: clamp(2.3rem, 6vw, 4.7rem);
  line-height: 0.98;
}

h2 {
  margin-bottom: 0.5rem;
  font-size: 1.35rem;
}

.intro p,
.panel-copy,
.file-meta span,
.summary-grid p,
.status-card p,
.status-panel {
  color: var(--muted);
}

.status-card,
.upload-panel,
.merge-panel,
.summary-grid article {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--surface), transparent 2%);
  box-shadow: var(--shadow);
}

.status-card {
  padding: 1rem;
}

.status-card span,
.summary-grid span {
  display: block;
  color: var(--coral);
  font-size: 2rem;
  font-weight: 900;
  line-height: 1;
}

.status-card p,
.summary-grid p {
  margin: 0.45rem 0 0;
}

.workspace-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(340px, 0.85fr);
  gap: 1rem;
  align-items: start;
}

.upload-panel,
.merge-panel {
  padding: 1rem;
}

.panel-heading {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: flex-start;
  margin-bottom: 0.8rem;
}

.drop-zone {
  display: grid;
  place-items: center;
  min-height: 170px;
  border: 1px dashed color-mix(in srgb, var(--accent), var(--line) 45%);
  border-radius: var(--radius);
  background: var(--accent-soft);
  color: var(--accent);
  cursor: pointer;
  margin-bottom: 1rem;
  padding: 1rem;
  text-align: center;
}

.drop-zone input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.drop-zone span {
  border-radius: var(--radius);
  background: var(--accent);
  color: #ffffff;
  font-weight: 900;
  padding: 0.7rem 1rem;
}

.drop-zone strong {
  display: block;
  margin-top: 0.65rem;
}

.drop-zone.is-dragging {
  outline: 3px solid color-mix(in srgb, var(--accent), transparent 45%);
}

.file-list {
  display: grid;
  gap: 0.55rem;
  max-height: 58vh;
  overflow: auto;
}

.empty-state {
  display: grid;
  min-height: 120px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--muted);
  text-align: center;
}

.file-row {
  display: grid;
  grid-template-columns: 64px minmax(0, 1fr) auto;
  gap: 0.75rem;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-strong);
  padding: 0.65rem;
}

.file-type {
  display: grid;
  width: 52px;
  height: 52px;
  place-items: center;
  border-radius: var(--radius);
  background: var(--ink);
  color: var(--surface);
  font-size: 0.78rem;
  font-weight: 900;
}

.file-meta {
  min-width: 0;
}

.file-meta strong,
.file-meta span {
  display: block;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.file-actions {
  display: flex;
  gap: 0.35rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.file-actions button {
  min-height: 34px;
  padding: 0.4rem 0.55rem;
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.48;
}

.field-grid {
  display: grid;
  gap: 0.8rem;
  margin: 1rem 0;
}

.field-grid label {
  display: grid;
  gap: 0.35rem;
}

.field-grid span {
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

select,
input[type="text"] {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  min-height: 42px;
  padding: 0.6rem 0.75rem;
}

.summary-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.6rem;
  margin: 1rem 0;
}

.summary-grid article {
  padding: 0.85rem;
  box-shadow: none;
}

.summary-grid span {
  font-size: 1.5rem;
  overflow-wrap: anywhere;
}

.merge-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.7rem;
  margin-bottom: 1rem;
}

.primary-action,
.download-action {
  display: inline-grid;
  place-items: center;
  background: var(--accent);
  border-color: var(--accent);
  color: #ffffff;
  min-height: 44px;
}

.download-action.is-disabled {
  pointer-events: none;
  opacity: 0.52;
}

.status-panel {
  min-height: 48px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-strong);
  padding: 0.8rem;
}

.status-panel.is-error {
  border-color: var(--coral);
  color: var(--coral);
  font-weight: 800;
}

@media (max-width: 980px) {
  .intro,
  .workspace-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .app-header,
  .app-header nav,
  .panel-heading,
  .merge-actions {
    align-items: stretch;
    flex-direction: column;
    grid-template-columns: 1fr;
  }

  .app-shell {
    padding-top: 2.5rem;
  }

  .file-row {
    grid-template-columns: 52px minmax(0, 1fr);
  }

  .file-actions {
    grid-column: 1 / -1;
    justify-content: stretch;
  }

  .file-actions button {
    flex: 1 1 auto;
  }

  .summary-grid {
    grid-template-columns: 1fr;
  }

  h1 {
    font-size: 2.5rem;
  }
}