/* ─── Tokens ─────────────────────────────────────────── */
:root {
  color-scheme: light;
  --font: "DM Sans", system-ui, -apple-system, sans-serif;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 2px rgba(15, 20, 25, 0.06), 0 4px 16px rgba(15, 20, 25, 0.06);
  --shadow-lg: 0 8px 32px rgba(15, 20, 25, 0.14);
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --header-h: 64px;

  --bg: #f4f6f8;
  --bg-elevated: #ffffff;
  --bg-muted: #eef1f4;
  --bg-hover: #e6eaef;
  --border: #dce2e8;
  --text: #1a2330;
  --text-muted: #5c6b7a;
  --text-faint: #8a97a5;
  --accent: #2f6fed;
  --accent-hover: #2559c7;
  --accent-soft: rgba(47, 111, 237, 0.12);
  --danger: #d64545;
  --danger-soft: rgba(214, 69, 69, 0.12);
  --success: #1f9d63;
  --warning: #c47a12;
  --col-backlog: #7c5cff;
  --col-doing: #2f6fed;
  --col-waiting: #ff8a3d;
  --col-done: #12b886;
  --col-backlog-bg: #f3efff;
  --col-doing-bg: #eaf1ff;
  --col-waiting-bg: #fff3e8;
  --col-done-bg: #e6faf3;
  --col-backlog-header: linear-gradient(135deg, #7c5cff 0%, #a78bfa 100%);
  --col-doing-header: linear-gradient(135deg, #2f6fed 0%, #60a5fa 100%);
  --col-waiting-header: linear-gradient(135deg, #ff8a3d 0%, #fbbf24 100%);
  --col-done-header: linear-gradient(135deg, #12b886 0%, #34d399 100%);
  --tag-bg: #e8eef8;
  --tag-text: #2f4a7a;
  --overdue: #d64545;
  --due-soon: #c47a12;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0f1419;
  --bg-elevated: #1a222c;
  --bg-muted: #151c24;
  --bg-hover: #243040;
  --border: #2a3544;
  --text: #e8eef4;
  --text-muted: #9aabbc;
  --text-faint: #6a7a8a;
  --accent: #5b8fff;
  --accent-hover: #7aa3ff;
  --accent-soft: rgba(91, 143, 255, 0.18);
  --danger: #f07178;
  --danger-soft: rgba(240, 113, 120, 0.16);
  --success: #3ecf8e;
  --warning: #e0a23a;
  --col-backlog: #a78bfa;
  --col-doing: #5b8fff;
  --col-waiting: #fbbf24;
  --col-done: #34d399;
  --col-backlog-bg: #1a1530;
  --col-doing-bg: #121c2e;
  --col-waiting-bg: #2a1f12;
  --col-done-bg: #10241c;
  --col-backlog-header: linear-gradient(135deg, #6d28d9 0%, #a78bfa 100%);
  --col-doing-header: linear-gradient(135deg, #2563eb 0%, #60a5fa 100%);
  --col-waiting-header: linear-gradient(135deg, #ea580c 0%, #fbbf24 100%);
  --col-done-header: linear-gradient(135deg, #059669 0%, #34d399 100%);
  --tag-bg: #243448;
  --tag-text: #b8cce8;
  --overdue: #f07178;
  --due-soon: #e0a23a;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 16px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.45);
}

/* ─── Reset ──────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  min-height: 100dvh;
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.45;
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(124, 92, 255, 0.18), transparent 60%),
    radial-gradient(900px 500px at 90% 0%, rgba(47, 111, 237, 0.14), transparent 55%),
    radial-gradient(800px 480px at 70% 110%, rgba(18, 184, 134, 0.12), transparent 50%),
    var(--bg);
  -webkit-font-smoothing: antialiased;
}
[data-theme="dark"] body {
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(167, 139, 250, 0.16), transparent 60%),
    radial-gradient(900px 500px at 90% 0%, rgba(91, 143, 255, 0.12), transparent 55%),
    radial-gradient(800px 480px at 70% 110%, rgba(52, 211, 153, 0.1), transparent 50%),
    var(--bg);
}
button, input, textarea, select {
  font: inherit;
  color: inherit;
}
button { cursor: pointer; }
h1, h2, p { margin: 0; }
em { font-style: normal; color: var(--text-faint); font-weight: 400; }

/* ─── App shell ──────────────────────────────────────── */
.app {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

.header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: var(--header-h);
  padding: 10px 16px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}
.logo {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 18px;
  flex-shrink: 0;
}
.header-brand h1 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
}
.subtitle {
  font-size: 0.75rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

/* ─── Buttons ────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  padding: 8px 14px;
  font-weight: 550;
  font-size: 0.9rem;
  background: var(--bg-muted);
  color: var(--text);
  transition: background 0.15s var(--ease), border-color 0.15s, color 0.15s, transform 0.1s;
}
.btn:hover { background: var(--bg-hover); }
.btn:active { transform: scale(0.98); }
.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover { background: var(--accent-hover); color: #fff; }
.btn-ghost {
  background: transparent;
  border-color: var(--border);
}
.btn-ghost:hover { background: var(--bg-muted); }
.btn-danger { color: var(--danger); }
.btn-danger:hover { background: var(--danger-soft); }
.btn-icon {
  width: 36px;
  height: 36px;
  padding: 0;
  font-size: 1.35rem;
  line-height: 1;
  background: transparent;
  border: none;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
}
.btn-icon:hover { background: var(--bg-muted); color: var(--text); }
.btn-sm {
  padding: 4px 8px;
  font-size: 0.8rem;
  min-width: 32px;
}

.theme-icon-moon { display: none; }
[data-theme="dark"] .theme-icon-sun { display: none; }
[data-theme="dark"] .theme-icon-moon { display: inline; }

/* ─── Board ──────────────────────────────────────────── */
.board {
  flex: 1;
  display: grid;
  grid-template-columns: repeat(4, minmax(260px, 1fr));
  gap: 14px;
  padding: 16px;
  overflow-x: auto;
  align-items: start;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
}

.column {
  display: flex;
  flex-direction: column;
  min-height: calc(100dvh - var(--header-h) - 48px);
  max-height: calc(100dvh - var(--header-h) - 32px);
  background: var(--bg-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  scroll-snap-align: start;
  overflow: hidden;
}
.column.drag-over {
  border-color: var(--accent);
  box-shadow: inset 0 0 0 1px var(--accent);
  background: color-mix(in srgb, var(--accent-soft) 40%, var(--bg-muted));
}

.column-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 14px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-elevated);
  flex-shrink: 0;
}
.column-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}
.column[data-col="backlog"] .column-dot { background: var(--col-backlog); }
.column[data-col="doing"] .column-dot { background: var(--col-doing); }
.column[data-col="waiting"] .column-dot { background: var(--col-waiting); }
.column[data-col="done"] .column-dot { background: var(--col-done); }

.column-title {
  font-size: 0.85rem;
  font-weight: 650;
  letter-spacing: 0.01em;
  flex: 1;
}
.column-count {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-muted);
  border-radius: 999px;
  min-width: 22px;
  height: 22px;
  display: grid;
  place-items: center;
  padding: 0 6px;
}

.column-cards {
  flex: 1;
  overflow-y: auto;
  padding: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-height: 80px;
}

.empty-state {
  margin: auto;
  text-align: center;
  padding: 24px 12px;
  color: var(--text-faint);
  font-size: 0.85rem;
  pointer-events: none;
  user-select: none;
}
.empty-state span {
  display: block;
  font-size: 1.5rem;
  margin-bottom: 6px;
  opacity: 0.6;
}

/* ─── Cards ──────────────────────────────────────────── */
.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px;
  box-shadow: var(--shadow);
  cursor: grab;
  transition: box-shadow 0.15s var(--ease), border-color 0.15s, transform 0.15s var(--ease);
  touch-action: manipulation;
}
.card:hover {
  border-color: color-mix(in srgb, var(--accent) 35%, var(--border));
}
.card:active { cursor: grabbing; }
.card.dragging {
  opacity: 0.45;
  transform: scale(0.98);
}
.card:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.card-title {
  font-weight: 600;
  font-size: 0.95rem;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
  word-break: break-word;
}
.card-notes {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  white-space: pre-wrap;
  word-break: break-word;
}
.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
  margin-bottom: 8px;
}
.tag {
  font-size: 0.7rem;
  font-weight: 550;
  padding: 2px 8px;
  border-radius: 999px;
  background: var(--tag-bg);
  color: var(--tag-text);
}
.due {
  font-size: 0.72rem;
  font-weight: 550;
  color: var(--text-muted);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}
.due.overdue { color: var(--overdue); }
.due.due-soon { color: var(--due-soon); }

.card-actions {
  display: flex;
  gap: 4px;
  margin-top: 4px;
  padding-top: 8px;
  border-top: 1px solid var(--border);
}
.card-actions .btn {
  flex: 1;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
}
.card-actions .btn:hover {
  background: var(--bg-muted);
  color: var(--text);
  border-color: var(--border);
}
.card-actions .btn:disabled {
  opacity: 0.3;
  cursor: not-allowed;
  pointer-events: none;
}

/* ─── Modal ──────────────────────────────────────────── */
.modal {
  border: none;
  border-radius: var(--radius);
  padding: 0;
  width: min(440px, calc(100vw - 24px));
  background: var(--bg-elevated);
  color: var(--text);
  box-shadow: var(--shadow-lg);
  max-height: calc(100dvh - 24px);
}
.modal::backdrop {
  background: rgba(10, 14, 20, 0.55);
  backdrop-filter: blur(4px);
}
.modal[open] {
  animation: modalIn 0.2s var(--ease);
}
@keyframes modalIn {
  from { opacity: 0; transform: translateY(8px) scale(0.98); }
  to { opacity: 1; transform: none; }
}
.modal-form { display: flex; flex-direction: column; }
.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 16px 0;
}
.modal-header h2 {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.modal-body {
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  overflow-y: auto;
}
.modal-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 0 16px 16px;
  flex-wrap: wrap;
}
.modal-footer-right {
  display: flex;
  gap: 8px;
  margin-left: auto;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.field > span {
  font-size: 0.8rem;
  font-weight: 550;
  color: var(--text-muted);
}
.field input,
.field textarea,
.field select {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  background: var(--bg);
  transition: border-color 0.15s, box-shadow 0.15s;
}
.field input:focus,
.field textarea:focus,
.field select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.field textarea { resize: vertical; min-height: 72px; }

/* ─── Toast ──────────────────────────────────────────── */
.toast {
  position: fixed;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 100;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 16px;
  border-radius: 999px;
  box-shadow: var(--shadow-lg);
  font-size: 0.85rem;
  font-weight: 500;
  max-width: calc(100vw - 32px);
}
.toast[hidden] { display: none; }

/* ─── Responsive ─────────────────────────────────────── */
@media (max-width: 900px) {
  .board {
    grid-template-columns: repeat(4, minmax(280px, 85vw));
    padding-bottom: 24px;
  }
  .column {
    min-height: calc(100dvh - var(--header-h) - 56px);
  }
  .header-brand .subtitle { display: none; }
  #addCardBtn span:first-child { margin: 0; }
  #addCardBtn { padding-inline: 12px; }
}

@media (max-width: 480px) {
  .header { padding-inline: 12px; }
  .board { padding: 12px; gap: 10px; }
  .btn-primary#addCardBtn {
    font-size: 0;
    gap: 0;
    width: 40px;
    height: 40px;
    padding: 0;
    border-radius: 10px;
  }
  .btn-primary#addCardBtn span {
    font-size: 1.35rem;
  }
}


/* ─── Colourful columns ──────────────────────────────── */
.column[data-col="backlog"] { background: var(--col-backlog-bg); border-color: color-mix(in srgb, var(--col-backlog) 35%, var(--border)); }
.column[data-col="doing"] { background: var(--col-doing-bg); border-color: color-mix(in srgb, var(--col-doing) 35%, var(--border)); }
.column[data-col="waiting"] { background: var(--col-waiting-bg); border-color: color-mix(in srgb, var(--col-waiting) 35%, var(--border)); }
.column[data-col="done"] { background: var(--col-done-bg); border-color: color-mix(in srgb, var(--col-done) 35%, var(--border)); }

.column[data-col="backlog"] .column-header,
.column[data-col="doing"] .column-header,
.column[data-col="waiting"] .column-header,
.column[data-col="done"] .column-header {
  color: #fff;
  border-bottom: none;
}
.column[data-col="backlog"] .column-header { background: var(--col-backlog-header); }
.column[data-col="doing"] .column-header { background: var(--col-doing-header); }
.column[data-col="waiting"] .column-header { background: var(--col-waiting-header); }
.column[data-col="done"] .column-header { background: var(--col-done-header); }

.column .column-header .column-dot {
  background: rgba(255,255,255,0.95) !important;
  box-shadow: 0 0 0 3px rgba(255,255,255,0.25);
}
.column .column-header .column-title { color: #fff; }
.column .column-header .column-count {
  background: rgba(255,255,255,0.22);
  color: #fff;
}

.card { border-top: 3px solid transparent; }
.column[data-col="backlog"] .card { border-top-color: var(--col-backlog); }
.column[data-col="doing"] .card { border-top-color: var(--col-doing); }
.column[data-col="waiting"] .card { border-top-color: var(--col-waiting); }
.column[data-col="done"] .card { border-top-color: var(--col-done); }