#shape-sum-grid {
  display: grid;
  grid-template-columns: repeat(5, 80px);
  grid-template-rows: repeat(5, 80px);
  gap: 4px;
  margin: 20px auto;
}

@media (max-width: 640px) {
  #shape-sum-grid {
    grid-template-columns: repeat(5, 60px);
    grid-template-rows: repeat(5, 60px);
    gap: 3px;
    margin: 10px auto;
  }
}

.grid-cell {
  width: 80px;
  height: 80px;
  border: 3px solid #5741AC;
  border-radius: 8px;
  background: white;
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  transition: all 0.2s;
  position: relative;
}

@media (max-width: 640px) {
  .grid-cell {
    width: 60px;
    height: 60px;
    border: 2px solid #5741AC;
    border-radius: 6px;
  }
}

.grid-cell:hover:not(.sum-cell):not(.disabled-cell) {
  background: #f0f0f0;
  transform: scale(1.05);
}

.grid-cell.focused {
  border: 4px solid #00A2FF;
  box-shadow: 0 0 10px rgba(0, 162, 255, 0.5);
}

.grid-cell.disabled-cell {
  pointer-events: none;
  opacity: 0.6;
}

.grid-cell.mystery-cell {
  background: linear-gradient(135deg, #f0f0f0 25%, transparent 25%, transparent 75%, #f0f0f0 75%),
              linear-gradient(135deg, #f0f0f0 25%, transparent 25%, transparent 75%, #f0f0f0 75%);
  background-size: 20px 20px;
  background-position: 0 0, 10px 10px;
  border: 3px dashed #999;
}

/* Sum cells - no border on outside edges */
.sum-cell {
  border: none;
  background: transparent;
  cursor: default;
  font-size: 32px;
  font-weight: bold;
  color: #5741AC;
  display: flex;
  justify-content: center;
  align-items: center;
}

@media (max-width: 640px) {
  .sum-cell {
    font-size: 24px;
  }
}

.sum-cell.mystery-sum {
  font-size: 48px;
  color: #999;
}

.sum-cell input {
  width: 60px;
  height: 50px;
  text-align: center;
  font-size: 32px;
  font-weight: bold;
  border: 3px solid #5741AC;
  border-radius: 8px;
  color: #5741AC;
  background: white;
}

@media (max-width: 640px) {
  .sum-cell input {
    width: 45px;
    height: 40px;
    font-size: 24px;
    border: 2px solid #5741AC;
  }
}

.sum-cell input:focus {
  outline: none;
  border-color: #00A2FF;
  box-shadow: 0 0 10px rgba(0, 162, 255, 0.5);
}

.mystery-sum-input {
  background: linear-gradient(135deg, #f0f0f0 25%, transparent 25%, transparent 75%, #f0f0f0 75%),
              linear-gradient(135deg, #f0f0f0 25%, transparent 25%, transparent 75%, #f0f0f0 75%) !important;
  background-size: 20px 20px !important;
  background-position: 0 0, 10px 10px !important;
  border: 3px dashed #999 !important;
}

.mystery-sum-input::placeholder {
  color: #999;
  font-size: 48px;
  opacity: 1;
}

/* Shape styles */
.shape {
  width: 50px;
  height: 50px;
}

@media (max-width: 640px) {
  .shape {
    width: 38px;
    height: 38px;
  }
}

.shape-triangle {
  width: 0;
  height: 0;
  border-left: 25px solid transparent;
  border-right: 25px solid transparent;
  border-bottom: 43px solid #4A90E2;
}

.shape-square {
  width: 45px;
  height: 45px;
  background: #4CAF50;
  border-radius: 4px;
}

.shape-pentagon {
  width: 45px;
  height: 43px;
  background: #5741AC;
  clip-path: polygon(50% 0%, 100% 38%, 82% 100%, 18% 100%, 0% 38%);
}

.shape-circle {
  width: 48px;
  height: 48px;
  background: #4ECDC4;
  border-radius: 50%;
}

.shape-star {
  width: 0;
  height: 0;
  border-left: 25px solid transparent;
  border-right: 25px solid transparent;
  border-bottom: 35px solid #F7DC6F;
  position: relative;
}

.shape-star::before {
  content: '';
  position: absolute;
  width: 0;
  height: 0;
  border-left: 25px solid transparent;
  border-right: 25px solid transparent;
  border-top: 35px solid #F7DC6F;
  top: 10px;
  left: -25px;
}

.shape-hexagon {
  width: 45px;
  height: 39px;
  background: #E67E22;
  clip-path: polygon(25% 0%, 75% 0%, 100% 50%, 75% 100%, 25% 100%, 0% 50%);
}

.shape-diamond {
  width: 40px;
  height: 40px;
  background: #E91E63;
  transform: rotate(45deg);
}

#stopwatch {
  margin: 10px;
  font-weight: bold;
  font-size: 24px;
}