/* Mask Overlay */
.mask {
  position: fixed;
  top: 0; 
  left: 0; 
  right: 0; 
  bottom: 0;
  background: rgba(0,0,0,0.5);
  z-index: 999;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}
.mask.show {
  opacity: 1;
  pointer-events: auto;
}

/* Sheet Modal (Now Centered Modal) */
.sheet {
  position: fixed;
  top: 50%;
  left: 50%;
  width: 600px;
  max-width: 90%;
  max-height: 85vh;
  background: #fff;
  z-index: 1000;
  transform: translate(-50%, -50%) scale(0.95);
  transition: all 0.3s cubic-bezier(0.2, 0.8, 0.2, 1);
  border-radius: 16px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.2);
  display: flex;
  flex-direction: column;
  opacity: 0;
  pointer-events: none;
}
.sheet.show {
  transform: translate(-50%, -50%) scale(1);
  opacity: 1;
  pointer-events: auto;
}

/* Sheet Header */
.sheet-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 24px;
  border-bottom: 1px solid #eee;
  flex-shrink: 0;
}
.sheet-title {
  font-size: 18px;
  font-weight: 800;
  color: #333;
}
.sheet-close {
  font-size: 24px;
  color: #999;
  cursor: pointer;
  line-height: 1;
  padding: 4px;
  transition: color 0.2s;
}
.sheet-close:hover {
  color: #333;
}

/* Sheet Body */
.sheet-bd {
  flex: 1;
  overflow-y: auto;
  padding: 24px;
}

/* Sheet Footer */
.sheet-footer {
  padding: 16px 24px;
  background: #fff;
  border-top: 1px solid #eee;
  flex-shrink: 0;
  border-bottom-left-radius: 16px;
  border-bottom-right-radius: 16px;
}

.st-title {
  margin: 0 0 12px 0;
  font-size: 18px;
  line-height: 1.4;
  color: #333;
}
.sheet-meta {
  font-size: 13px;
  color: #999;
  margin-bottom: 16px;
}

.sheet-accept {
  background: #f5f7fa;
  padding: 12px;
  border-radius: 8px;
  margin-bottom: 24px;
}
.acc-label {
  font-size: 12px;
  font-weight: 700;
  color: #666;
  margin-bottom: 4px;
  text-transform: uppercase;
}

.sheet-actions {
  display: flex;
  gap: 12px;
}
.btn-act {
  flex: 1;
  padding: 12px;
  border: none;
  border-radius: 8px;
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
}
.btn-primary { background: var(--blue); color: #fff; }
.btn-success { background: var(--green); color: #fff; }
.btn-danger { background: var(--red); color: #fff; }
.btn-warning { background: var(--orange); color: #fff; }
.btn-default { background: #eee; color: #333; }

/* Subtask Files Section */
.st-files-section {
  margin-bottom: 24px;
  background: #fdfdfd;
  border: 1px solid #eee;
  border-radius: 8px;
  padding: 12px;
}
.sec-subtitle {
  font-size: 13px;
  font-weight: 700;
  color: #666;
  margin-bottom: 8px;
}
.file-row-simple {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 0;
  border-bottom: 1px solid #f5f5f5;
}
.file-row-simple:last-child {
  border-bottom: none;
}
.fr-icon { font-size: 20px; }
.fr-info { flex: 1; }
.fr-name { font-size: 13px; color: #333; margin-bottom: 2px; }
.fr-meta { font-size: 11px; color: #999; }