:root {
    --background-color: #1a1a1a;
    --surface-color: #2c2c2c;
    --primary-color: #00aaff;
    --primary-hover: #0088cc;
    --text-color: #f0f0f0;
    --text-secondary: #a0a0a0;
    --border-color: #444;
    --error-color: #ff4d4d;
}
body {
    font-family: 'Noto Sans KR', sans-serif;
    margin: 0;
    background-color: var(--background-color);
    color: var(--text-color);
}
.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 1.5rem;
}
header {
    padding: 1.5rem 0;
    border-bottom: 1px solid var(--border-color);
}
header .logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
}
main {
    padding: 3rem 0;
}
.hero {
    text-align: center;
}
.hero h1 {
    font-size: 3rem;
    background: -webkit-linear-gradient(45deg, #00aaff, #ffffff);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}
.hero p {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
}
.resizer-tool {
    background-color: var(--surface-color);
    border-radius: 12px;
    padding: 2.5rem;
    border: 1px solid var(--border-color);
    box-shadow: 0 8px 32px rgba(0,0,0,0.2);
}
.upload-area {
    border: 2px dashed var(--border-color);
    border-radius: 8px;
    padding: 3rem;
    text-align: center;
    cursor: pointer;
    transition: background-color 0.3s, border-color 0.3s;
}
.upload-area:hover {
    background-color: #333;
    border-color: var(--primary-color);
}
.upload-instructions {
    font-weight: 500;
    color: var(--text-secondary);
}
.upload-instructions strong {
    color: var(--primary-color);
}
.image-preview-container {
    margin-top: 2rem;
    text-align: center;
}
.image-preview {
    max-width: 100%;
    max-height: 350px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    margin-bottom: 2rem;
}
.controls-wrapper {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}
.presets-container {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  align-items: center;
}
.preset-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  justify-content: center;
}
.preset-button {
  background-color: #3a3a3a;
  color: var(--text-color);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.2s;
}
.preset-button:hover {
  background-color: var(--primary-color);
  color: #fff;
  border-color: var(--primary-color);
}
.dimensions-controls {
    display: flex;
    gap: 1rem;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
}
.input-group {
    display: flex;
    align-items: center;
    background-color: var(--background-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.25rem 0.75rem;
}
.input-group label {
    margin-right: 0.5rem;
    font-weight: 500;
    color: var(--text-secondary);
}
.input-group input {
    width: 80px;
    padding: 0.5rem;
    border: none;
    background-color: transparent;
    color: var(--text-color);
    font-size: 1rem;
    text-align: center;
    outline: none;
}
input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 
}
.lock-button {
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
}
.lock-button svg {
    width: 24px;
    height: 24px;
    fill: var(--text-secondary);
    transition: fill 0.2s;
}
.lock-button:hover svg,
.lock-button.locked svg {
    fill: var(--primary-color);
}
.format-selector {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.75rem;
    margin-top: 1rem;
    flex-wrap: wrap;
}
.format-selector label {
    color: var(--text-secondary);
    font-weight: 500;
}
.format-button {
  background-color: #3a3a3a;
  color: var(--text-color);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.2s;
}
.format-button:hover {
  border-color: var(--primary-color);
}
.format-button.active {
  background-color: var(--primary-color);
  color: #fff;
  border-color: var(--primary-color);
}
.action-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-top: 1rem;
    flex-wrap: wrap;
}
.action-button {
    background-color: var(--primary-color);
    color: white;
    padding: 0.8rem 2rem;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s;
    position: relative;
    overflow: hidden;
}
.action-button:hover {
    background-color: var(--primary-hover);
}
.action-button.secondary {
    background-color: #555;
}
.action-button.secondary:hover {
    background-color: #666;
}
.action-button:disabled {
    background-color: #444;
    color: #888;
    cursor: not-allowed;
}
.error-message {
    color: var(--error-color);
    margin-top: 1.5rem;
    font-weight: 500;
}
.ad-placeholder {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    text-align: center;
    padding: 2rem;
    margin: 3rem auto;
    color: var(--text-secondary);
    border-radius: 12px;
}
.horizontal-ad { 
    height: 90px; 
    margin-top: 0;
    margin-bottom: 2.5rem;
}
.section-title {
    text-align: center;
    font-size: 2.2rem;
    margin-bottom: 3rem;
    color: var(--text-color);
}
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    text-align: center;
}
 .feature-item {
    background-color: var(--surface-color);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}
.feature-item h3 {
    font-size: 1.3rem;
    color: var(--primary-color);
}
 .feature-item p {
    color: var(--text-secondary);
}
.footer {
    text-align: center;
    padding: 2rem 0;
    border-top: 1px solid var(--border-color);
    margin-top: 2rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
}
@media (max-width: 768px) {
    .hero h1 { font-size: 2.2rem; }
    .hero p { font-size: 1rem; }
    .resizer-tool { padding: 1.5rem; }
}
.share-buttons-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1rem;
}
.share-button {
    border: none;
    border-radius: 8px;
    padding: 0.8rem 1.5rem;
    font-size: 1rem;
    font-weight: 500;
    color: #fff;
    cursor: pointer;
    transition: opacity 0.2s;
    min-width: 120px;
}
.share-button:hover {
    opacity: 0.85;
}
.share-button.naver { background-color: #03C75A; }
.share-button.facebook { background-color: #1877F2; }
.share-button.x { background-color: #000000; border: 1px solid #fff; }
.share-button.band { background-color: #00c73c; }
.share-button.threads { background-color: #000000; border: 1px solid #fff; }
.share-button.copy-url { background-color: #555; }