*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Noto Sans JP", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: #333;
  background: #f4f6fa;
}

/* ========== HEADER ========== */
.site-header {
  background: linear-gradient(135deg, #1a2340 0%, #2c3e6b 100%);
  color: white;
  padding: 1rem 1rem 1.25rem;
  text-align: center;
  position: relative;
}

.back-link {
  display: inline-block;
  position: absolute;
  left: 1rem;
  top: 1rem;
  color: rgba(255,255,255,0.75);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color 0.2s;
  min-height: 44px;
  line-height: 44px;
}

.back-link:hover {
  color: #fff;
}

.site-header h1 {
  font-size: 1.1rem;
  margin-top: 0.25rem;
  line-height: 1.4;
  padding: 0 2rem;
}

.subtitle {
  font-size: 0.85rem;
  opacity: 0.8;
  margin-top: 0.4rem;
}

/* ========== MAIN ========== */
main {
  max-width: 780px;
  margin: 0 auto;
  padding: 1rem;
}

/* ========== AD UNIT ========== */
.ad-unit {
  margin: 1.25rem 0;
}

/* ========== TOOL SECTION ========== */
.tool-section {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.step-block {
  background: #fff;
  border-radius: 12px;
  padding: 1.25rem;
  box-shadow: 0 1px 6px rgba(0,0,0,0.07);
}

.step-title {
  font-size: 1rem;
  font-weight: 700;
  color: #1a2340;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: #4a90e2;
  color: white;
  border-radius: 50%;
  font-size: 0.85rem;
  font-weight: 800;
  flex-shrink: 0;
}

/* ========== DROP ZONE ========== */
.drop-zone {
  border: 2px dashed #b0c4de;
  border-radius: 10px;
  background: #f7f9ff;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
  min-height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.drop-zone:hover,
.drop-zone.drag-over {
  border-color: #4a90e2;
  background: #eef4ff;
}

.drop-zone-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  padding: 1.5rem;
  text-align: center;
}

.drop-zone-text {
  font-size: 0.95rem;
  color: #555;
  line-height: 1.5;
}

.drop-zone-text span {
  font-size: 0.85rem;
  color: #888;
}

.file-label {
  display: inline-block;
  padding: 0.6rem 1.5rem;
  background: #4a90e2;
  color: white;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 600;
  min-height: 44px;
  line-height: 44px;
  padding-top: 0;
  padding-bottom: 0;
  transition: background 0.2s;
}

.file-label:hover {
  background: #357abd;
}

#file-input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.upload-status {
  margin-top: 0.5rem;
  font-size: 0.875rem;
  color: #4caf50;
  min-height: 1.2em;
}

.upload-status.error {
  color: #e53935;
}

/* ========== DEVICE SELECTOR ========== */
.device-selector {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
}

.device-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  padding: 0.85rem 0.5rem;
  background: #f4f6fa;
  border: 2px solid #dde3ef;
  border-radius: 10px;
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  color: #444;
  transition: border-color 0.2s, background 0.2s;
  min-height: 80px;
}

.device-btn:hover {
  border-color: #4a90e2;
  background: #eef4ff;
}

.device-btn.active {
  border-color: #4a90e2;
  background: #eef4ff;
  color: #1a5fb4;
}

/* Device mini icons (CSS-drawn) */
.device-icon {
  display: block;
  position: relative;
}

/* iPhone icon */
.device-icon-iphone {
  width: 22px;
  height: 36px;
  border: 2.5px solid currentColor;
  border-radius: 5px;
  background: #fff;
}
.device-icon-iphone::before {
  content: '';
  position: absolute;
  top: 3px;
  left: 50%;
  transform: translateX(-50%);
  width: 8px;
  height: 2.5px;
  background: currentColor;
  border-radius: 2px;
}
.device-icon-iphone::after {
  content: '';
  position: absolute;
  bottom: 3px;
  left: 50%;
  transform: translateX(-50%);
  width: 6px;
  height: 6px;
  border: 1.5px solid currentColor;
  border-radius: 50%;
}

/* iPad icon */
.device-icon-ipad {
  width: 36px;
  height: 28px;
  border: 2.5px solid currentColor;
  border-radius: 4px;
  background: #fff;
}
.device-icon-ipad::after {
  content: '';
  position: absolute;
  top: 50%;
  right: -6px;
  transform: translateY(-50%);
  width: 3px;
  height: 10px;
  background: currentColor;
  border-radius: 0 2px 2px 0;
}

/* MacBook icon */
.device-icon-macbook {
  width: 36px;
  height: 24px;
  border: 2.5px solid currentColor;
  border-radius: 3px 3px 0 0;
  background: #fff;
}
.device-icon-macbook::before {
  content: '';
  position: absolute;
  bottom: -5px;
  left: -4px;
  width: 44px;
  height: 4px;
  background: currentColor;
  border-radius: 0 0 2px 2px;
}

/* Browser icon */
.device-icon-browser {
  width: 38px;
  height: 28px;
  border: 2.5px solid currentColor;
  border-radius: 4px;
  background: #fff;
}
.device-icon-browser::before {
  content: '';
  position: absolute;
  top: 4px;
  left: 0;
  right: 0;
  height: 7px;
  background: currentColor;
  border-radius: 1px 1px 0 0;
  opacity: 0.25;
}
.device-icon-browser::after {
  content: '';
  position: absolute;
  top: 6px;
  left: 5px;
  width: 14px;
  height: 3px;
  background: #fff;
  border-radius: 2px;
}

/* ========== OPTIONS ========== */
.options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.option-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.option-group.full-width {
  grid-column: 1 / -1;
}

.option-group label {
  font-size: 0.875rem;
  font-weight: 600;
  color: #333;
}

.bg-type-selector {
  display: flex;
  gap: 0.4rem;
}

.bg-btn {
  flex: 1;
  padding: 0.45rem 0.25rem;
  background: #f4f6fa;
  border: 1.5px solid #dde3ef;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
  min-height: 44px;
}

.bg-btn:hover {
  border-color: #4a90e2;
}

.bg-btn.active {
  border-color: #4a90e2;
  background: #eef4ff;
  color: #1a5fb4;
}

#bg-color,
#grad-color1,
#grad-color2 {
  width: 100%;
  height: 44px;
  border: 1.5px solid #dde3ef;
  border-radius: 6px;
  padding: 2px 4px;
  cursor: pointer;
  background: none;
}

.gradient-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.gradient-row input[type="color"] {
  flex: 1;
}

.grad-arrow {
  font-size: 1rem;
  color: #888;
  flex-shrink: 0;
}

#scale-slider {
  width: 100%;
  accent-color: #4a90e2;
  height: 6px;
  cursor: pointer;
}

/* ========== PREVIEW ========== */
.preview-area {
  position: relative;
  background: #e8edf6;
  border-radius: 10px;
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  margin-bottom: 1rem;
}

#preview-canvas {
  max-width: 100%;
  max-height: 480px;
  border-radius: 6px;
  display: none;
  object-fit: contain;
}

.preview-placeholder {
  color: #aaa;
  font-size: 0.9rem;
  text-align: center;
  padding: 2rem;
}

/* ========== ACTION BUTTONS ========== */
.action-buttons {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.btn-primary,
.btn-download {
  flex: 1;
  min-width: 140px;
  padding: 0 1rem;
  height: 56px;
  font-size: 1rem;
  font-weight: 700;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: opacity 0.2s, transform 0.1s;
}

.btn-primary:not(:disabled):hover,
.btn-download:not(:disabled):hover {
  opacity: 0.88;
}

.btn-primary:not(:disabled):active,
.btn-download:not(:disabled):active {
  transform: scale(0.97);
}

.btn-primary {
  background: #2c3e6b;
  color: white;
}

.btn-download {
  background: #27ae60;
  color: white;
}

.btn-primary:disabled,
.btn-download:disabled {
  opacity: 0.38;
  cursor: not-allowed;
}

/* ========== HOWTO ========== */
.howto-section {
  background: white;
  border-radius: 12px;
  padding: 1.5rem;
  margin-top: 1.5rem;
  box-shadow: 0 1px 6px rgba(0,0,0,0.07);
}

.howto-section h2 {
  font-size: 1.05rem;
  color: #1a2340;
  margin-bottom: 0.75rem;
  margin-top: 1.25rem;
}

.howto-section h2:first-child {
  margin-top: 0;
}

.howto-section ol,
.howto-section p {
  font-size: 0.93rem;
  color: #555;
  line-height: 1.7;
}

.howto-section ol {
  padding-left: 1.25rem;
}

.howto-section li {
  margin-bottom: 0.6rem;
}

/* ========== FOOTER ========== */
.site-footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.85rem;
  color: #888;
  margin-top: 1.5rem;
}

.site-footer a {
  color: #666;
  text-decoration: none;
}

.site-footer a:hover {
  text-decoration: underline;
}

/* ========== RESPONSIVE ========== */
@media (min-width: 640px) {
  .site-header h1 {
    font-size: 1.4rem;
    padding: 0 4rem;
  }

  main {
    padding: 1.5rem 2rem;
  }

  .device-selector {
    grid-template-columns: repeat(4, 1fr);
  }

  .step-block {
    padding: 1.5rem 1.75rem;
  }
}

@media (max-width: 400px) {
  .options-grid {
    grid-template-columns: 1fr;
  }
}