:root {
  --bg-gradient: linear-gradient(135deg, #f8fafc, #e2e8f0);
  --text-color: #0f172a;
  --sub-text-color: #475569;
  --container-bg: rgba(255, 255, 255, 0.95);
  --container-shadow: 0 20px 50px rgba(15, 23, 42, 0.12);
  --set-bg: #f8fafc;
  --set-border: #e2e8f0;
  --set-title-color: #1e293b;
  --footer-text: #64748b;
  --button-bg: #2563eb;
  --button-text: #ffffff;
}

[data-theme="dark"] {
  --bg-gradient: linear-gradient(135deg, #0f172a, #1e293b);
  --text-color: #f8fafc;
  --sub-text-color: #94a3b8;
  --container-bg: rgba(30, 41, 59, 0.95);
  --container-shadow: 0 20px 50px rgba(0, 0, 0, 0.3);
  --set-bg: #1e293b;
  --set-border: #334155;
  --set-title-color: #f1f5f9;
  --footer-text: #94a3b8;
  --button-bg: #3b82f6;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, "Apple SD Gothic Neo", "Noto Sans KR", sans-serif;
  background: var(--bg-gradient);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  color: var(--text-color);
  transition: background 0.3s ease, color 0.3s ease;
}

.container {
  width: 100%;
  max-width: 760px;
  background: var(--container-bg);
  border-radius: 24px;
  box-shadow: var(--container-shadow);
  padding: 32px;
  position: relative;
  transition: background 0.3s ease, box-shadow 0.3s ease;
}

.theme-toggle {
  position: absolute;
  top: 20px;
  right: 20px;
}

#themeBtn {
  background: none;
  border: 1px solid var(--set-border);
  color: var(--text-color);
  padding: 8px 12px;
  font-size: 0.9rem;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s ease;
}

#themeBtn:hover {
  background: var(--set-bg);
}

h1 {
  margin: 0 0 10px;
  font-size: 2rem;
  text-align: center;
}

.sub {
  margin: 0 0 28px;
  text-align: center;
  color: var(--sub-text-color);
  line-height: 1.6;
}

.actions {
  display: flex;
  justify-content: center;
  margin-bottom: 28px;
}

#generateBtn {
  border: none;
  background: var(--button-bg);
  color: var(--button-text);
  font-size: 1rem;
  font-weight: 700;
  padding: 14px 24px;
  border-radius: 14px;
  cursor: pointer;
  transition: transform 0.15s ease, opacity 0.15s ease, background 0.3s ease;
}

#generateBtn:hover {
  transform: translateY(-1px);
  opacity: 0.95;
}

#generateBtn:active {
  transform: translateY(1px);
}

.results {
  display: grid;
  gap: 14px;
}

.set {
  background: var(--set-bg);
  border: 1px solid var(--set-border);
  border-radius: 18px;
  padding: 16px;
  transition: background 0.3s ease, border-color 0.3s ease;
}

.set-title {
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--set-title-color);
}

.balls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.ball {
  width: 48px;
  height: 48px;
  border-radius: 999px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: white;
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.12);
}

.range-1-10 { background: #f59e0b; }
.range-11-20 { background: #3b82f6; }
.range-21-30 { background: #ef4444; }
.range-31-40 { background: #6b7280; }
.range-41-45 { background: #22c55e; }

.divider {
  margin: 40px 0;
  border: 0;
  border-top: 1px solid var(--set-border);
}

.partnership-section {
  margin-top: 20px;
}

.partnership-section h3 {
  text-align: center;
  margin-bottom: 8px;
  color: var(--text-color);
}

.form-sub {
  text-align: center;
  font-size: 0.9rem;
  color: var(--sub-text-color);
  margin-bottom: 24px;
}

.partnership-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 500px;
  margin: 0 auto;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group label {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-color);
}

.form-group input,
.form-group textarea {
  padding: 12px;
  border-radius: 10px;
  border: 1px solid var(--set-border);
  background: var(--set-bg);
  color: var(--text-color);
  font-family: inherit;
  font-size: 0.95rem;
  transition: border-color 0.2s;
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--button-bg);
}

.form-group textarea {
  min-height: 120px;
  resize: vertical;
}

.submit-btn {
  border: none;
  background: var(--button-bg);
  color: var(--button-text);
  font-size: 1rem;
  font-weight: 700;
  padding: 14px;
  border-radius: 12px;
  cursor: pointer;
  transition: transform 0.15s ease, opacity 0.15s ease;
  margin-top: 8px;
}

.submit-btn:hover {
  opacity: 0.9;
  transform: translateY(-1px);
}

.footer {
  margin-top: 24px;
  text-align: center;
  color: var(--footer-text);
  font-size: 0.95rem;
}

@media (max-width: 640px) {
  .container {
    padding: 22px;
  }

  h1 {
    font-size: 1.6rem;
  }

  .ball {
    width: 42px;
    height: 42px;
  }

  .theme-toggle {
    top: 10px;
    right: 10px;
  }
}