/* 기본 리셋 및 변수 */
:root {
  --bg: #f8f9fa;
  --surface: #ffffff;
  --text: #1a1a2e;
  --text-sub: #6b7280;
  --primary: #667eea;
  --primary-hover: #5a6fd6;
  --border: #e5e7eb;
  --radius: 12px;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f0f23;
    --surface: #1a1a2e;
    --text: #e2e8f0;
    --text-sub: #94a3b8;
    --border: #2d2d44;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
  }
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.6;
}

/* 헤더 */
header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
}

nav {
  max-width: 800px;
  margin: 0 auto;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--primary);
  text-decoration: none;
}

/* 메인 */
main {
  flex: 1;
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
  width: 100%;
}

h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.subtitle {
  color: var(--text-sub);
  margin-bottom: 1.5rem;
}

/* 모드 탭 */
.mode-tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}

.mode-tab {
  padding: 0.4rem 1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text-sub);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.mode-tab:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.mode-tab.active {
  background: var(--primary);
  border-color: var(--primary);
  color: white;
}

/* 입력 섹션 */
.input-section {
  margin-bottom: 1rem;
}

.input-section[hidden] {
  display: none;
}

textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-family: inherit;
  font-size: 0.95rem;
  resize: vertical;
  line-height: 1.5;
  transition: border-color 0.2s;
}

textarea:focus {
  outline: none;
  border-color: var(--primary);
}

.form-group {
  margin-bottom: 0.75rem;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-sub);
  margin-bottom: 0.25rem;
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.9rem;
  font-family: inherit;
  transition: border-color 0.2s;
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary);
}

/* 옵션 */
.options {
  display: flex;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.options label {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-sub);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.range-wrapper {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.range-wrapper input[type="range"] {
  width: 150px;
  accent-color: var(--primary);
}

.range-wrapper span {
  font-weight: 600;
  color: var(--text);
  min-width: 5ch;
}

/* 생성 버튼 */
.btn-generate {
  width: 100%;
  padding: 0.75rem;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-generate:hover {
  background: var(--primary-hover);
}

/* 결과 */
.result {
  margin-top: 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.result[hidden] {
  display: none;
}

#qr-canvas {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.btn-download {
  padding: 0.6rem 1.5rem;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-download:hover {
  background: var(--primary-hover);
}

/* 푸터 */
footer {
  padding: 1.5rem;
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-sub);
  border-top: 1px solid var(--border);
}

/* 반응형 */
@media (max-width: 480px) {
  main {
    padding: 1.5rem 1rem;
  }

  .options {
    flex-direction: column;
    gap: 1rem;
  }
}