:root {
  --bg: #f3f4f6;
  --card: #ffffff;
  --text: #111827;
  --subtext: #6b7280;
  --input: #ffffff;
  --border: #d1d5db;
  --button: #2563eb;
  --button-hover: #1d4ed8;
  --copy-bg: #e5e7eb;
  --copy-text: #111827;
}

body.dark {
  --bg: #111827;
  --card: #1f2937;
  --text: #f9fafb;
  --subtext: #9ca3af;
  --input: #374151;
  --border: #4b5563;
  --copy-bg: #374151;
  --copy-text: #f9fafb;
}

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

body {
  min-height: 100vh;
  font-family: Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.3s ease, color 0.3s ease;
}

.container {
  width: 100%;
  padding: 20px;
}

.card {
  max-width: 430px;
  margin: 0 auto;
  background: var(--card);
  color: var(--text);
  padding: 28px;
  border-radius: 18px;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.25);
  transition: background 0.3s ease, color 0.3s ease;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 16px;
  margin-bottom: 24px;
}

h1 {
  font-size: 28px;
  margin-bottom: 8px;
}

.header p {
  color: var(--subtext);
  line-height: 1.4;
}

.theme-btn {
  width: 42px;
  height: 42px;
  border: none;
  border-radius: 50%;
  background: var(--copy-bg);
  color: var(--copy-text);
  font-size: 20px;
  cursor: pointer;
}

.result-box {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
}

.result-box input {
  flex: 1;
  min-width: 0;
  padding: 13px;
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: 15px;
  background: var(--input);
  color: var(--text);
  outline: none;
}

button {
  border: none;
  cursor: pointer;
  border-radius: 10px;
  font-weight: 600;
}

#copyBtn {
  padding: 0 14px;
  background: var(--copy-bg);
  color: var(--copy-text);
}

.setting {
  margin-bottom: 18px;
}

.setting label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
}

.setting input {
  width: 100%;
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--input);
  color: var(--text);
  outline: none;
}

.options {
  display: grid;
  gap: 12px;
  margin-bottom: 22px;
}

.options label {
  display: flex;
  gap: 10px;
  align-items: center;
  color: var(--text);
}

.generate-btn {
  width: 100%;
  padding: 14px;
  background: var(--button);
  color: white;
  font-size: 16px;
}

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

#message {
  margin-top: 14px;
  text-align: center;
  font-size: 14px;
  color: #16a34a;
  min-height: 20px;
}