body {
  font-family: "Inter", sans-serif;
  background-color: #f6f8fa;
  color: #24292e;
  margin: 0;
  padding: 0;
}

header {
  text-align: center;
  padding: 2rem 1rem;
  background: #24292e;
  color: #fff;
}

header h1 {
  margin: 0;
  font-size: 1.8rem;
}

.back-link {
  display: inline-block;
  margin-top: 1rem;
  color: #58a6ff;
  text-decoration: none;
}

.back-link:hover {
  text-decoration: underline;
}

.tool-container {
  padding: 2rem;
}

.card {
  background: #fff;
  max-width: 960px;
  margin: 2rem auto;
  padding: 2rem;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

/* Buttons */
.btn-group {
  display: flex;
  justify-content: flex-start;
  gap: 0.8rem;
  margin-bottom: 1rem;
}

button {
  background-color: #2da44e;
  color: white;
  border: none;
  padding: 0.8rem 1.5rem;
  font-size: 1rem;
  border-radius: 8px;
  cursor: pointer;
}

button:hover {
  background-color: #2c974b;
}

.secondary {
  background-color: #6e7781;
}

.secondary:hover {
  background-color: #5a616a;
}

/* Diff container for input textareas */
.diff-container {
  display: flex;
  gap: 1rem;
  margin-top: 1rem;
  flex-wrap: wrap; /* stack on small screens */
}

.diff-column {
  flex: 1;
  display: flex;
  flex-direction: column;
}

.diff-column h3 {
  margin-bottom: 0.5rem;
}

.diff-column textarea {
  width: 100%;
  min-height: 200px;
  padding: 0.8rem;
  font-size: 1rem;
  border-radius: 8px;
  border: 1px solid #d0d7de;
  resize: vertical;
}

/* Diff result section */
.diff-result {
  display: flex;
  gap: 1rem;
  margin-top: 2rem;
}

.diff-side {
  flex: 1;
  background: #f6f8fa;
  border: 1px solid #d0d7de;
  border-radius: 8px;
  padding: 1rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
  max-height: 600px;
}

.diff-line {
  white-space: pre-wrap;
  word-break: break-word;
  margin-bottom: 2px;
}

.diff-removed {
  background-color: #ffeef0; /* light red */
}

.diff-added {
  background-color: #e6ffed; /* light green */
}

.char-removed {
  background-color: #fdd; /* inline removed chars */
}

.char-added {
  background-color: #cfc; /* inline added chars */
}

footer {
  text-align: center;
  padding: 1rem;
  background: #f1f3f5;
  color: #555;
  margin-top: 2rem;
}

/* Responsive layout */
@media (max-width: 768px) {
  .diff-result,
  .diff-container {
    flex-direction: column;
  }
}

@media (max-width: 500px) {
  .btn-group {
    flex-direction: column;
    width: 100%;
  }
  .btn-group button {
    width: 100%;
  }
}