.hidden {
  display: none !important;
}

#date-nav {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

#prevBtn,
#nextBtn {
  font-size: 1.2rem;
  color: #95a5a6;
  text-decoration: none;
  line-height: 1;
  transition: color 0.15s;
}

#prevBtn:hover,
#nextBtn:hover {
  color: #2c3d51;
}

#solved-check {
  color: #27ae60;
  font-weight: 700;
}

#date-label {
  font-size: 0.9rem;
  color: #95a5a6;
  font-family: system-ui, sans-serif;
}

#error-area {
  text-align: center;
  padding: 2rem 1rem;
}

#error-area p {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 1.3rem;
  color: #f22952;
  margin: 0;
}

#game {
  max-width: 480px;
  margin: 0 auto;
  padding: 1rem 1.25rem 3rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  min-height: calc(100vh - 56px);
}

#target-area {
  text-align: center;
}

#target-label {
  margin: 0 0 0.25rem;
  font-size: 0.95rem;
  color: #95a5a6;
  text-transform: uppercase;
  letter-spacing: 1px;
}

#target-number {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 4rem;
  font-weight: 700;
  color: #2c3d51;
  line-height: 1;
}

#numbers-area {
  width: 100%;
}

#tiles {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  justify-content: center;
}

.tile {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 1.4rem;
  font-weight: 600;
  width: 64px;
  height: 64px;
  border-radius: 12px;
  border: 2px solid transparent;
  background: #fff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.09);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition:
    transform 0.1s,
    box-shadow 0.1s,
    background 0.1s,
    opacity 0.15s;
  color: #2c3d51;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  position: relative;
}

.tile:hover:not(.used):not(.selected) {
  transform: translateY(-2px);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.13);
}

.tile.selected {
  background: #f22952;
  color: #fff;
  border-color: #f22952;
  box-shadow: 0 4px 14px rgba(242, 41, 82, 0.3);
}

.tile.derived {
  background: #fff8f0;
  border-color: #ff7043;
}

.tile.derived.selected {
  background: #f22952;
  border-color: #f22952;
  color: #fff;
}

.tile.used {
  opacity: 0.25;
  cursor: default;
  pointer-events: none;
}

.tile.target-hit {
  background: #27ae60;
  color: #fff;
  border-color: #27ae60;
  animation: pop 0.35s ease;
}

@keyframes pop {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.2);
  }
  100% {
    transform: scale(1);
  }
}

#ops-area {
  display: flex;
  gap: 0.75rem;
}

.op-btn {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 1.5rem;
  font-weight: 600;
  width: 60px;
  height: 60px;
  border-radius: 12px;
  border: 2px solid #e0dbd4;
  background: #fff;
  color: #2c3d51;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition:
    background 0.1s,
    border-color 0.1s,
    transform 0.1s;
  -webkit-tap-highlight-color: transparent;
}

.op-btn:hover {
  border-color: #aaa;
}

.op-btn.selected {
  background: #2c3d51;
  border-color: #2c3d51;
  color: #fff;
}

#expression-area {
  font-size: 1.1rem;
  color: #555;
  font-family: "Fredoka", system-ui, sans-serif;
  font-weight: 600;
  letter-spacing: 0.5px;
}

#expression:empty::after {
  content: " ";
}

#history-area {
  width: 100%;
}

#history-list {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  align-items: center;
}

.history-entry {
  font-size: 1rem;
  color: #95a5a6;
  font-family: "Fredoka", system-ui, sans-serif;
  font-weight: 600;
}

#action-area {
  display: flex;
  gap: 0.75rem;
}

#action-area button {
  padding: 0.55rem 1.2rem;
  border-radius: 10px;
  border: 2px solid #e0dbd4;
  background: #fff;
  color: #2c3d51;
  font-size: 0.9rem;
  font-family: system-ui, sans-serif;
  cursor: pointer;
  transition:
    border-color 0.15s,
    opacity 0.15s;
}

#action-area button:hover:not(:disabled) {
  border-color: #aaa;
}

#action-area button:disabled {
  opacity: 0.35;
  cursor: default;
}

#solved-banner {
  position: fixed;
  inset: 0;
  background: rgba(251, 249, 246, 0.92);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  z-index: 10;
  animation: fadeIn 0.3s ease;
}

#solved-banner span {
  font-size: 4rem;
}

#solved-banner p {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 2rem;
  font-weight: 700;
  color: #2c3d51;
  margin: 0 0 1rem;
}

#solved-banner.hidden {
  display: none;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

#solution-overlay {
  position: fixed;
  inset: 0;
  background: rgba(44, 61, 81, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 20;
  animation: fadeIn 0.2s ease;
  padding: 1.5rem;
}

#solution-overlay.hidden {
  display: none;
}

#solution-box {
  background: #fff;
  border-radius: 16px;
  padding: 1.75rem 2rem;
  max-width: 340px;
  width: 100%;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.18);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

#solution-title {
  margin: 0;
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 1.1rem;
  font-weight: 700;
  color: #95a5a6;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.solution-step {
  font-family: "Fredoka", system-ui, sans-serif;
  font-size: 1.3rem;
  font-weight: 600;
  color: #2c3d51;
}

#solution-close {
  margin-top: 0.5rem;
  padding: 0.5rem 1.2rem;
  border-radius: 10px;
  border: 2px solid #e0dbd4;
  background: #fff;
  color: #2c3d51;
  font-size: 0.9rem;
  cursor: pointer;
  align-self: flex-end;
}

#solution-close:hover {
  border-color: #aaa;
}