:root {
  --bg: #f3f5fa;
  --panel: #ffffff;
  --ink: #1a2236;
  --muted: #6a7388;
  --border: #e3e7f0;
  --accent: #2563eb;
  --accent-ink: #ffffff;
  --accent-soft: #dbe7ff;
  --free: #ecfdf3;
  --free-border: #b6e6c8;
  --free-ink: #1c7a44;
  --taken: #f1f3f8;
  --taken-ink: #4d5670;
  --mine: #fff4d6;
  --mine-border: #f0d97a;
  --mine-ink: #7a5a00;
  --err: #b3261e;
  --ok: #1f7a3a;
  --shadow: 0 8px 24px rgba(20, 30, 60, 0.12);
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font: 15px/1.45 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  min-height: 100vh;
}

header {
  text-align: center;
  padding: 28px 16px 8px;
}
header h1 { margin: 0; font-size: 26px; letter-spacing: -0.01em; }
header .subtitle { margin: 4px 0 0; color: var(--muted); font-size: 14px; }

main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 16px;
}

/* Day strip */
#day-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding: 14px 4px;
  margin: 8px 0 4px;
}

.day-pill {
  flex: 1 1 110px;
  border: 1px solid var(--border);
  background: #fff;
  border-radius: 10px;
  padding: 10px 14px;
  cursor: pointer;
  text-align: center;
  transition: border-color 0.12s, background 0.12s, transform 0.06s;
}
.day-pill:hover { border-color: var(--accent); }
.day-pill:active { transform: scale(0.98); }
.day-pill .wd { display: block; font-size: 11px; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); }
.day-pill .dm { display: block; font-size: 18px; font-weight: 600; margin-top: 2px; }
.day-pill .y  { display: block; font-size: 11px; color: var(--muted); margin-top: 1px; }
.day-pill.active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-ink);
}
.day-pill.active .wd, .day-pill.active .y { color: rgba(255,255,255,0.85); }

.day-info {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 16px;
  margin: 6px 0 14px;
  font-size: 14px;
}
.day-info .di-title {
  font-weight: 600;
  color: var(--ink);
  font-size: 15px;
  margin-bottom: 4px;
}
.day-info .di-times {
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 8px;
}
.day-info .di-exams-label {
  color: var(--muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 4px;
}
.day-info ul.di-exams {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.day-info ul.di-exams li {
  background: var(--accent-soft);
  color: var(--accent);
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 12.5px;
  font-weight: 500;
}
.day-info .di-no-exams {
  color: var(--muted);
  font-size: 13px;
  font-style: italic;
}

/* Grid */
#grid-wrap {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 8px;
  overflow-x: auto;
}
table#grid {
  width: 100%;
  border-collapse: separate;
  border-spacing: 6px;
  min-width: 540px;
}
table#grid th {
  font-size: 12px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 600;
  padding: 8px 4px;
  text-align: center;
}
table#grid th.hour-col { text-align: left; padding-left: 8px; }
table#grid td {
  padding: 0;
  vertical-align: middle;
}
.hour-cell {
  font-weight: 600;
  font-size: 14px;
  color: var(--ink);
  padding: 0 8px;
  white-space: nowrap;
}

/* Cells */
.slot {
  width: 100%;
  min-height: 56px;
  border: 1px solid transparent;
  border-radius: 8px;
  padding: 8px 10px;
  font: inherit;
  text-align: left;
  cursor: pointer;
  transition: transform 0.06s, box-shadow 0.12s, border-color 0.12s;
  display: block;
}
.slot.free {
  background: var(--free);
  border-color: var(--free-border);
  color: var(--free-ink);
  text-align: center;
  font-weight: 600;
}
.slot.free:hover {
  box-shadow: 0 2px 8px rgba(28, 122, 68, 0.15);
  border-color: var(--free-ink);
}
.slot.free:active { transform: scale(0.985); }
.slot.taken {
  background: var(--taken);
  color: var(--taken-ink);
  cursor: default;
}
.slot .who {
  font-weight: 600;
  font-size: 13px;
  display: block;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.slot .why {
  font-size: 12px;
  color: var(--muted);
  display: block;
  margin-top: 2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.legend {
  text-align: center;
  color: var(--muted);
  font-size: 13px;
  margin: 18px 0 24px;
  display: flex;
  justify-content: center;
  gap: 18px;
  flex-wrap: wrap;
}
.swatch {
  display: inline-block;
  width: 14px;
  height: 14px;
  border-radius: 4px;
  vertical-align: -2px;
  margin-right: 4px;
  border: 1px solid var(--border);
}
.swatch.free  { background: var(--free); border-color: var(--free-border); }
.swatch.taken { background: var(--taken); }
.legend-note { text-align: center; color: var(--muted); font-size: 12px; margin: -10px 0 24px; }

.help { color: var(--muted); text-align: center; padding: 24px; }

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(20, 30, 60, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  z-index: 100;
}
.modal[hidden] { display: none; }
.modal-card {
  background: #fff;
  border-radius: 14px;
  width: 100%;
  max-width: 440px;
  padding: 22px;
  box-shadow: var(--shadow);
  position: relative;
}
.modal-card h2 { margin: 0 0 4px; font-size: 18px; }
.modal-summary {
  margin: 0 0 16px;
  padding: 10px 12px;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 8px;
  font-weight: 600;
  font-size: 14px;
}
.modal-close {
  position: absolute;
  top: 8px;
  right: 10px;
  background: transparent;
  border: 0;
  color: var(--muted);
  font-size: 24px;
  line-height: 1;
  cursor: pointer;
  padding: 4px 8px;
}
.modal-card form label {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin-bottom: 12px;
  font-size: 13px;
  color: var(--muted);
}
.modal-card input,
.modal-card textarea {
  font: inherit;
  color: var(--ink);
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  resize: vertical;
}
.modal-card input:focus,
.modal-card textarea:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: var(--accent);
}
.modal-actions {
  display: flex;
  gap: 8px;
  justify-content: flex-end;
  margin-top: 8px;
}
.modal-actions button {
  font: inherit;
  border-radius: 8px;
  padding: 10px 16px;
  cursor: pointer;
  border: 0;
}
#modal-submit {
  background: var(--accent);
  color: var(--accent-ink);
}
#modal-submit:hover { filter: brightness(1.05); }
#modal-submit:disabled { opacity: 0.6; cursor: not-allowed; }
.btn-ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--border) !important;
}
.btn-ghost:hover { background: var(--bg); }
.msg { font-size: 13px; margin: 10px 0 0; min-height: 1em; }
.msg.err { color: var(--err); }
.msg.ok  { color: var(--ok); }

/* Toast */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--ink);
  color: #fff;
  padding: 12px 18px;
  border-radius: 10px;
  font-size: 14px;
  box-shadow: var(--shadow);
  z-index: 200;
  max-width: 92vw;
  text-align: center;
}
.toast.err { background: var(--err); }
.toast.ok  { background: var(--ok); }

@media (max-width: 560px) {
  header { padding-top: 18px; }
  header h1 { font-size: 22px; }
  table#grid { border-spacing: 4px; }
  .slot { min-height: 50px; padding: 6px 8px; }
  .slot .who { font-size: 12px; }
  .slot .why { display: none; }
  .hour-cell { font-size: 13px; padding: 0 4px; }
}