/* ========== Reset & Base ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --primary: #1677ff;
  --primary-dark: #0958d9;
  --primary-light: #e6f4ff;
  --bg: #ffffff;
  --bg-secondary: #f5f7fa;
  --text: #1a1a2e;
  --text-secondary: #666;
  --text-muted: #999;
  --border: #e8e8e8;
  --radius: 12px;
  --shadow: 0 2px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
}

html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }

a { color: var(--primary); text-decoration: none; }
a:hover { opacity: 0.8; }

/* ========== Header ========== */
.header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 64px;
}
.logo { display: flex; align-items: center; gap: 8px; }
.logo-icon { font-size: 28px; }
.logo-img { width: 32px; height: 32px; border-radius: 6px; object-fit: contain; max-width: 32px; max-height: 32px; }
.logo-text { font-size: 20px; font-weight: 700; color: var(--text); }
.nav { display: flex; align-items: center; gap: 24px; flex-shrink: 0; }
.nav a { font-size: 15px; color: var(--text-secondary); transition: color 0.2s; white-space: nowrap; }
.nav a:hover { color: var(--primary); opacity: 1; }
.btn-donate {
  padding: 6px 18px; border-radius: 20px;
  background: var(--primary); color: #fff !important;
  font-weight: 500;
}
.lang-switch {
  padding: 4px 12px; border: 1px solid var(--border);
  border-radius: 16px; font-size: 13px !important;
}

/* ========== Hero ========== */
.hero {
  padding: 80px 0 60px;
  background: linear-gradient(135deg, #f0f5ff 0%, #e6f4ff 50%, #f5f0ff 100%);
}
.hero .container { display: flex; align-items: center; gap: 60px; }
.hero-content { flex: 1; }
.hero-title { font-size: 42px; font-weight: 800; line-height: 1.3; margin-bottom: 16px; }
.hero-name-cn { display: block; color: var(--text); }
.hero-name-en { display: block; color: var(--primary); font-size: 36px; }
.hero-subtitle { font-size: 20px; color: var(--text-secondary); margin-bottom: 16px; }
.hero-desc { font-size: 16px; color: var(--text-muted); margin-bottom: 32px; line-height: 1.8; }
.hero-buttons { display: flex; gap: 16px; }
.hero-image { flex: 1; display: flex; justify-content: center; }
.hero-mockup {
  width: 320px; height: 500px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 30px; padding: 20px;
  box-shadow: var(--shadow-lg);
  display: flex; align-items: center; justify-content: center;
}
.mockup-screen {
  width: 100%; height: 100%;
  background: rgba(255,255,255,0.15);
  border-radius: 20px; padding: 24px;
  display: flex; flex-direction: column; gap: 20px;
  justify-content: center;
}
.mockup-chord {
  background: rgba(255,255,255,0.2);
  padding: 16px; border-radius: 12px;
  font-size: 18px; font-weight: 700; color: #fff;
  text-align: center; font-family: monospace;
  word-break: break-all; overflow: hidden;
}
.mockup-tracks { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; }
.track {
  padding: 8px 14px; border-radius: 20px;
  font-size: 13px; color: #fff; font-weight: 500;
}
.track.vocal { background: rgba(255,107,107,0.7); }
.track.guitar { background: rgba(78,205,196,0.7); }
.track.bass { background: rgba(69,183,209,0.7); }
.track.drum { background: rgba(240,147,251,0.7); }
.track.piano { background: rgba(255,217,61,0.7); }

/* ========== Buttons ========== */
.btn {
  display: inline-block; padding: 12px 28px;
  border-radius: 8px; font-size: 16px; font-weight: 600;
  text-align: center; cursor: pointer; border: none;
  transition: all 0.2s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); opacity: 1; }
.btn-outline { background: transparent; color: var(--primary); border: 2px solid var(--primary); }
.btn-outline:hover { background: var(--primary-light); opacity: 1; }
.btn-sm { padding: 8px 20px; font-size: 14px; }
.btn-lg { padding: 16px 48px; font-size: 18px; border-radius: 12px; }

/* ========== Sections ========== */
section { padding: 80px 0; }
.section-title {
  font-size: 32px; font-weight: 700; text-align: center;
  margin-bottom: 12px;
}
.section-desc { text-align: center; color: var(--text-secondary); font-size: 16px; margin-bottom: 48px; }

/* ========== Features ========== */
.features { background: var(--bg); }
.features-grid {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px;
}
.feature-card {
  padding: 32px 24px; border-radius: var(--radius);
  background: var(--bg-secondary); border: 1px solid var(--border);
  transition: transform 0.2s, box-shadow 0.2s;
}
.feature-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.feature-icon { font-size: 40px; margin-bottom: 16px; }
.feature-card h3 { font-size: 18px; font-weight: 600; margin-bottom: 8px; }
.feature-card p { font-size: 14px; color: var(--text-secondary); line-height: 1.7; }

/* ========== Download ========== */
.download { background: var(--bg-secondary); }
.download-grid {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px;
}
.download-card {
  padding: 32px 20px; border-radius: var(--radius);
  background: var(--bg); border: 1px solid var(--border);
  text-align: center; transition: transform 0.2s, box-shadow 0.2s;
}
.download-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.download-icon { font-size: 40px; margin-bottom: 12px; }
.download-card h3 { font-size: 18px; font-weight: 600; margin-bottom: 8px; }
.download-card p { font-size: 13px; color: var(--text-muted); margin-bottom: 16px; }

/* ========== Donate Page ========== */
.donate-page { padding: 60px 0; background: var(--bg-secondary); min-height: calc(100vh - 64px - 200px); }
.donate-page-content { max-width: 640px; margin: 0 auto; }
.donate-page-desc { text-align: center; color: var(--text-secondary); font-size: 15px; line-height: 1.8; margin-bottom: 40px; }
.donate-amounts { margin-bottom: 40px; }
.donate-amounts h3, .donate-payment h3 { font-size: 18px; font-weight: 600; margin-bottom: 16px; }
.amount-grid { display: flex; gap: 12px; margin-bottom: 16px; flex-wrap: wrap; }
.amount-item {
  flex: 1; min-width: 80px; padding: 16px 12px;
  border: 2px solid var(--border); border-radius: 12px;
  text-align: center; cursor: pointer; transition: all 0.2s;
  background: var(--bg);
}
.amount-item:hover { border-color: var(--primary); }
.amount-item.active { border-color: var(--primary); background: var(--primary-light); }
.amount-value { display: block; font-size: 22px; font-weight: 700; color: var(--text); }
.amount-label { display: block; font-size: 12px; color: var(--text-muted); margin-top: 4px; }
.custom-amount { display: flex; align-items: center; gap: 12px; }
.custom-amount-label { font-size: 14px; color: var(--text-secondary); white-space: nowrap; }
.custom-amount-input {
  flex: 1; height: 44px; padding: 0 16px;
  border: 2px solid var(--border); border-radius: 10px;
  font-size: 16px; outline: none; transition: border-color 0.2s;
}
.custom-amount-input:focus { border-color: var(--primary); }

.donate-payment { margin-bottom: 40px; }
.payment-methods { display: flex; gap: 12px; }
.payment-method {
  padding: 12px 24px; border: 2px solid var(--border);
  border-radius: 12px; cursor: pointer; transition: all 0.2s;
  display: flex; align-items: center; gap: 8px; font-size: 15px;
  background: var(--bg);
}
.payment-method:hover { border-color: var(--primary); }
.payment-method.active { border-color: var(--primary); background: var(--primary-light); }
.payment-icon { font-size: 20px; }

.donate-action { text-align: center; margin-bottom: 40px; }
.donate-note { margin-top: 12px; font-size: 13px; color: var(--text-muted); }

.donate-qr { text-align: center; margin-top: 40px; padding: 40px; background: var(--bg); border-radius: var(--radius); }
.donate-qr h3 { font-size: 18px; margin-bottom: 24px; }
.qr-container { display: flex; justify-content: center; }
.qr-placeholder {
  padding: 40px; border: 2px dashed var(--border); border-radius: var(--radius);
  text-align: center; max-width: 400px;
}
.qr-icon { font-size: 48px; margin-bottom: 16px; }
.qr-placeholder p { font-size: 14px; color: var(--text-secondary); line-height: 1.8; }

/* ========== Footer ========== */
.footer { background: var(--text); color: #fff; padding: 40px 0; }
.footer-inner { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 16px; }
.footer-brand { display: flex; align-items: center; gap: 8px; font-size: 18px; font-weight: 600; }
.footer-links { display: flex; gap: 24px; }
.footer-links a { color: rgba(255,255,255,0.7); font-size: 14px; }
.footer-links a:hover { color: #fff; opacity: 1; }
.footer-copy p { font-size: 13px; color: rgba(255,255,255,0.5); }
.footer-icp { margin-top: 6px; }
.footer-icp a { color: rgba(255,255,255,0.4); font-size: 12px; }
.footer-icp a:hover { color: rgba(255,255,255,0.7); opacity: 1; }

/* ========== Responsive ========== */
@media (max-width: 768px) {
  .hero .container { flex-direction: column; gap: 40px; text-align: center; }
  .hero-title { font-size: 32px; }
  .hero-name-en { font-size: 28px; }
  .hero-buttons { justify-content: center; }
  .hero-mockup { width: 260px; height: 400px; }
  .features-grid { grid-template-columns: 1fr; }
  .download-grid { grid-template-columns: repeat(2, 1fr); }
  .header-inner { padding: 0 12px; }
  .nav { gap: 12px; }
  .nav a { font-size: 13px; }
  .amount-grid { flex-wrap: wrap; }
  .amount-item { min-width: 60px; }
}
@media (max-width: 480px) {
  .download-grid { grid-template-columns: 1fr; }
  .hero-mockup { width: 260px; height: 280px; }
  .mockup-screen { padding: 16px; gap: 12px; }
  .mockup-chord { font-size: 14px; padding: 10px; }
  .track { padding: 6px 10px; font-size: 11px; }
}
@media (max-width: 400px) {
  .header-inner { padding: 0 6px; height: 48px; }
  .logo { gap: 4px; }
  .logo img { width: 24px !important; height: 24px !important; }
  .logo-text { font-size: 14px; }
  .nav { gap: 6px; }
  .nav a { font-size: 10px; }
  .btn-donate { padding: 3px 8px; font-size: 10px; border-radius: 14px; }
  .lang-switch { padding: 2px 6px; font-size: 10px !important; }
  .hero { padding: 40px 0 30px; }
  .hero .container { gap: 24px; }
  .hero-title { font-size: 26px; }
  .hero-name-en { font-size: 22px; }
  .hero-subtitle { font-size: 16px; }
  .hero-desc { font-size: 14px; margin-bottom: 20px; }
  .hero-mockup { width: 240px; height: 240px; }
  .mockup-screen { padding: 12px; gap: 10px; }
  .mockup-chord { font-size: 12px; padding: 8px; }
  .mockup-tracks { gap: 6px; }
  .track { padding: 5px 8px; font-size: 10px; }
  .hero-buttons { flex-direction: column; gap: 10px; align-items: center; }
  .hero-buttons .btn { width: 100%; max-width: 200px; }
}