/* ===== 水印工坊样式表 ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  background: #f5f7fb;
  color: #1e1f2a;
  line-height: 1.5;
  min-height: 100vh;
  padding: 20px;
}

/* 返回首页按钮 */
.back-home-btn {
  position: fixed;
  top: 20px;
  right: 20px;
  left: auto;
  display: flex;
  align-items: center;
  gap: 6px;
  background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
  color: white;
  text-decoration: none;
  padding: 10px 18px;
  border-radius: 50px;
  font-size: 0.9rem;
  font-weight: 600;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
  transition: all 0.3s ease;
  z-index: 1000;
}

.back-home-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.4);
  background: linear-gradient(135deg, #1d4ed8 0%, #2563eb 100%);
}

.back-icon {
  font-size: 1.1rem;
}

@media (max-width: 720px) {
  .back-home-btn {
    top: 15px;
    right: 15px;
    left: auto;
    padding: 8px 14px;
    font-size: 0.85rem;
  }
}

.app {
  max-width: 1400px;
  margin: 0 auto;
}

h1 {
  font-size: 1.8rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 8px;
  color: #1f2937;
  letter-spacing: -0.01em;
}

h1::before {
  content: "🖼️";
  font-size: 2rem;
}

.main-panel {
  display: flex;
  flex-wrap: wrap;
  gap: 24px;
}

/* 左侧控制区 */
.control-panel {
  flex: 1 1 360px;
  min-width: 320px;
  background: #ffffffdd;
  backdrop-filter: blur(8px);
  background: rgba(255,255,255,0.9);
  border-radius: 28px;
  padding: 24px 20px;
  box-shadow: 0 10px 30px -5px rgba(0,0,0,0.05), 0 2px 8px rgba(0,0,0,0.03);
  border: 1px solid #ffffff80;
  height: fit-content;
}

/* 预览区 */
.preview-panel {
  flex: 2 1 500px;
  min-width: 300px;
  background: #ffffffcc;
  backdrop-filter: blur(8px);
  background: rgba(255,255,255,0.85);
  border-radius: 28px;
  padding: 20px;
  box-shadow: 0 10px 30px -5px rgba(0,0,0,0.05);
  border: 1px solid #ffffff80;
  display: flex;
  flex-direction: column;
}

.preview-title {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 12px;
  font-weight: 500;
  color: #374151;
}

.preview-container {
  background: #eef1f5;
  border-radius: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 320px;
  flex: 1;
  border: 1px dashed #cbd5e1;
  transition: border 0.2s;
  overflow: hidden;
}

canvas#previewCanvas {
  max-width: 100%;
  max-height: 100%;
  display: block;
  border-radius: 16px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  object-fit: contain;
}

.upload-area {
  margin-bottom: 28px;
}

.upload-box {
  border: 2px dashed #9aa4b8;
  border-radius: 20px;
  padding: 18px 16px;
  text-align: center;
  background: #fafcff;
  transition: border 0.2s, background 0.2s;
  cursor: pointer;
}

.upload-box.dragover {
  border-color: #2563eb;
  background: #eef4ff;
}

.upload-box p {
  margin: 6px 0;
  color: #475569;
  font-size: 0.95rem;
}

.file-info {
  font-size: 0.85rem;
  color: #2563eb;
  margin-top: 8px;
  word-break: break-all;
}

input[type="file"] {
  display: none;
}

.section {
  margin-top: 24px;
  border-top: 1px solid #e2e8f0;
  padding-top: 18px;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}

.section-header h3 {
  font-weight: 600;
  font-size: 1.2rem;
  color: #0f172a;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.9rem;
  color: #334155;
}

.form-group {
  margin-bottom: 16px;
}

.form-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

label {
  font-size: 0.9rem;
  font-weight: 500;
  color: #334155;
  min-width: 70px;
}

input[type="text"],
input[type="number"],
select {
  flex: 1;
  padding: 10px 12px;
  border: 1px solid #d1d9e6;
  border-radius: 16px;
  font-size: 0.95rem;
  background: white;
  transition: border 0.15s;
}

input:focus, select:focus {
  outline: none;
  border-color: #2563eb;
  box-shadow: 0 0 0 3px #2563eb20;
}

input[type="color"] {
  width: 60px;
  height: 42px;
  padding: 2px;
  border-radius: 16px;
  border: 1px solid #d1d9e6;
  background: white;
}

.slider-block {
  display: flex;
  align-items: center;
  gap: 12px;
}

.slider-block input[type="range"] {
  flex: 1;
  height: 6px;
  border-radius: 10px;
  background: #d9e2ef;
}

.value-badge {
  min-width: 45px;
  text-align: right;
  font-weight: 500;
}

/* 九宫格 */
.grid-9 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  max-width: 200px;
  margin: 10px 0;
}

.grid-btn {
  background: white;
  border: 1px solid #cbd5e1;
  border-radius: 14px;
  padding: 10px 0;
  font-size: 1rem;
  font-weight: 500;
  color: #1e293b;
  cursor: pointer;
  transition: all 0.15s;
  box-shadow: 0 2px 4px rgba(0,0,0,0.02);
}

.grid-btn:hover {
  background: #2563eb;
  color: white;
  border-color: #2563eb;
}

.offset-inputs {
  display: flex;
  gap: 16px;
  margin-top: 10px;
}

.offset-inputs label {
  min-width: auto;
}

.btn-download {
  width: 100%;
  margin-top: 30px;
  padding: 16px 20px;
  background: #1e293b;
  color: white;
  font-weight: 600;
  font-size: 1.1rem;
  border: none;
  border-radius: 40px;
  cursor: pointer;
  transition: background 0.2s, transform 0.1s;
  box-shadow: 0 8px 18px -6px #1e293b60;
}

.btn-download:hover {
  background: #0f172a;
}

.btn-download:active {
  transform: scale(0.98);
}

.note {
  font-size: 0.8rem;
  color: #64748b;
  margin-top: 8px;
  text-align: center;
}

/* 移动端调整 */
@media (max-width: 720px) {
  body { padding: 12px; }
  .main-panel { flex-direction: column; }
  .control-panel, .preview-panel { width: 100%; }
}