/* Calendar Card Stack — Overlay Framework
   Spec: docs/superpowers/specs/2026-04-03-calendar-overlay-framework-and-event-layer-design.md
   Z-index budget: 11-14 (above .tl-busy at 10, below .tl-block at 150)
   All colors via CSS variables — no hardcoded values. */

/* ═══ Card base ═══ */
.card-stack-card {
  position: absolute;
  left: 0;
  overflow: hidden;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  transform-origin: bottom left;
  will-change: transform;
  pointer-events: auto;
  /* Width set by JS: columnWidth - DECK_OFFSET for front cards, columnWidth for last */
}

/* Spring transition — applied by JS on flip, removed during drag */
.card-stack-card.card-spring {
  transition: transform 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275), box-shadow 0.4s ease;
}
@media (prefers-reduced-motion: reduce) {
  .card-stack-card.card-spring { transition: none !important; }
}

/* ═══ Compositing tiers (spec Section 2.5) ═══ */

/* Tier 1: User's own confirmed — most opaque glass, editable */
.card-stack-card.card-tier-own {
  background: color-mix(in srgb, var(--theme-primary, #667eea) 80%, transparent);
  -webkit-backdrop-filter: blur(16px);
  backdrop-filter: blur(16px);
  border: 1px solid color-mix(in srgb, var(--theme-primary, #667eea) 40%, transparent);
  border-radius: 6px;
  color: var(--theme-text-on-primary, #fff);
  box-shadow: 0 2px 8px rgba(0,0,0,0.3), inset 0 1px 0 rgba(255,255,255,0.1);
}
.card-stack-card.card-tier-own.card-active {
  box-shadow: 0 6px 28px color-mix(in srgb, var(--theme-primary, #667eea) 50%, transparent),
              inset 0 1px 0 rgba(255,255,255,0.15);
}

/* Tier 2: User's optional / invite — glass, dashed border */
.card-stack-card.card-tier-optional {
  background: color-mix(in srgb, var(--theme-primary, #667eea) 40%, transparent);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border: 2px dashed color-mix(in srgb, var(--theme-primary, #667eea) 40%, transparent);
  border-radius: 6px;
  color: var(--theme-text, #e2e8f0);
}

/* Tier 3: Public event — glass, read-only, accent border */
.card-stack-card.card-tier-public {
  background: color-mix(in srgb, var(--theme-surface, #1a1a2e) 60%, transparent);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border: 1px solid var(--theme-border, rgba(255,255,255,0.15));
  border-left: 3px solid var(--theme-accent, #22c55e);
  border-radius: 6px;
  color: var(--theme-text, #e2e8f0);
}
.card-stack-card.card-tier-public.card-active {
  box-shadow: 0 6px 24px color-mix(in srgb, var(--theme-accent, #22c55e) 30%, transparent);
}

/* Postponed: reduced opacity (spec Section 4.1) */
.card-stack-card.card-postponed {
  opacity: 0.5;
}

/* ═══ Tier 4: Merged opaque block — squared corners, striped (spec Section 2.5, 5.7) ═══ */
.card-stack-merged {
  position: absolute;
  left: 0; right: 0;
  z-index: 11;
  pointer-events: none;
  overflow: hidden;
  /* NO border-radius — squared corners, except at timeline edges */
}
.card-stack-merged .merged-stripe {
  position: absolute; inset: 0;
  background: repeating-linear-gradient(
    135deg,
    color-mix(in srgb, var(--theme-text, #9CA3AF) 8%, transparent) 0px,
    color-mix(in srgb, var(--theme-text, #9CA3AF) 8%, transparent) 4px,
    transparent 4px,
    transparent 8px
  );
  filter: blur(1.5px);
  opacity: 0.6;
}
.card-stack-merged .merged-glass {
  position: absolute; inset: 0;
  -webkit-backdrop-filter: blur(6px);
  backdrop-filter: blur(6px);
  background: color-mix(in srgb, var(--theme-surface, #1a1a2e) 30%, transparent);
}
.card-stack-merged .merged-label {
  position: relative; z-index: 1;
  padding: 4px 8px;
  font-size: 0.6rem;
  opacity: 0.5;
  color: var(--theme-text-muted, #888);
}
/* Timeline edge rounding (matches existing .at-timeline-top/bottom = 9px) */
.card-stack-merged.at-timeline-top {
  border-top-left-radius: 9px;
  border-top-right-radius: 9px;
}
.card-stack-merged.at-timeline-bottom {
  border-bottom-left-radius: 9px;
  border-bottom-right-radius: 9px;
}

/* ═══ Card content ═══ */
.card-stack-card .card-title {
  font-size: 0.65rem; font-weight: 600;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  position: relative; z-index: 1;
  padding: 4px 6px 0;
}
.card-stack-card .card-time {
  font-size: 0.5rem; opacity: 0.7; font-weight: 400;
  position: relative; z-index: 1;
  padding: 0 6px;
}
.card-stack-card .card-badge {
  font-size: 0.45rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px;
  padding: 1px 5px; border-radius: 3px; align-self: flex-start;
  margin: 4px 0 0 6px;
  background: var(--theme-accent, #22c55e);
  color: var(--theme-text-on-primary, #fff);
  position: relative; z-index: 1;
}
.card-stack-card .card-detail {
  font-size: 0.5rem; opacity: 0; margin-top: auto;
  position: relative; z-index: 1; transition: opacity 0.2s;
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
  padding: 0 6px 2px;
}
.card-stack-card .card-actions {
  display: flex; gap: 4px; padding: 2px 6px 4px;
  opacity: 0; transition: opacity 0.2s;
  position: relative; z-index: 1;
}
.card-stack-card .card-actions button {
  font-size: 0.5rem; padding: 2px 8px; border-radius: 4px;
  border: 1px solid var(--theme-border, rgba(255,255,255,0.2));
  background: color-mix(in srgb, var(--theme-surface, #1a1a2e) 80%, transparent);
  color: var(--theme-text, #fff); cursor: pointer; font-weight: 600;
}

/* Active card shows details + actions */
.card-stack-card.card-active .card-detail { opacity: 0.7; }
.card-stack-card.card-active .card-actions { opacity: 1; }

/* ═══ External calendar color accent (spec Section 2.5) ═══ */
.card-stack-card .card-ext-color {
  position: absolute; top: 4px; right: 4px;
  width: 6px; height: 6px; border-radius: 50%;
  z-index: 2;
}

/* ═══ Flyer background (spec Section 4.7) ═══ */
.card-stack-card .card-flyer-bg {
  position: absolute; inset: 0;
  background-size: cover; background-position: center;
  border-radius: inherit;
}
.card-stack-card .card-flyer-gradient {
  position: absolute; inset: 0;
  background: linear-gradient(to bottom, rgba(0,0,0,0.2), rgba(0,0,0,0.7));
  border-radius: inherit;
}

/* ═══ Soft zone timeline treatment (spec Section 6) ═══ */
.soft-zone {
  position: absolute;
  left: 0; right: 0;
  background: color-mix(in srgb, var(--theme-warning, #f59e0b) 5%, transparent);
  pointer-events: none;
  z-index: 1;
}

/* Soft zone warning on booking block during drag (spec Section 6.2) */
.tl-block.soft-zone-warning {
  border-color: var(--theme-warning, #f59e0b) !important;
}
.tl-block.soft-zone-warning::after {
  content: '\26A0  Sound advisory';
  position: absolute; bottom: 4px; left: 50%; transform: translateX(-50%);
  font-size: 0.5rem; color: var(--theme-warning, #f59e0b);
  white-space: nowrap; z-index: 5;
}

/* ═══ Hit area for gesture interaction ═══ */
.card-stack-hit {
  position: absolute;
  left: 0; right: 0;
  z-index: 14; /* above cards (11-13), below selection block (150) */
  cursor: pointer;
  outline: none; /* styled via card-active instead */
}
.card-stack-hit:focus-visible {
  outline: 2px solid var(--theme-primary, #667eea);
  outline-offset: 2px;
}

/* ═══ Popover for Month/Year desktop (spec Section 7.1) ═══ */
.card-stack-popover {
  position: fixed;
  z-index: 1000;
  background: var(--theme-surface, #1e1e2e);
  border: 1px solid var(--theme-border, #333);
  border-radius: 8px;
  padding: 8px;
  min-width: 200px;
  max-width: 300px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.3);
}