/* Reset */
* {
  margin: 0; 
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
  background-color: #121212;
  color: #eee;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header#header {
  background: linear-gradient(90deg, #0f2027, #203a43, #2c5364);
  padding: 1rem 2rem;
  text-align: center;
  box-shadow: 0 4px 8px rgba(0,0,0,0.4);
}

header#header h1 {
  font-weight: 700;
  font-size: 1.8rem;
  margin-bottom: 0.2rem;
  color: #00ffea;
  text-shadow: 0 0 8px #00ffe0;
}

header#header .subtitle {
  font-size: 0.9rem;
  color: #a0a0a0;
  font-style: italic;
}

#tabs {
  display: flex;
  background-color: #1e1e1e;
  border-bottom: 2px solid #333;
  justify-content: center;
}

.tab-btn {
  background: none;
  border: none;
  color: #bbb;
  padding: 1rem 2rem;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.3s ease;
  border-bottom: 3px solid transparent;
}

.tab-btn:hover,
.tab-btn:focus {
  color: #00ffea;
  outline: none;
}

.tab-btn.active {
  color: #00ffe0;
  border-bottom: 3px solid #00ffe0;
  font-weight: 600;
}

main {
  flex-grow: 1;
  padding: 1rem 2rem;
  background-color: #1e1e1e;
  display: flex;
  flex-direction: column;
}

#editor {
  height: 500px;
  border-radius: 6px;
  box-shadow: 0 0 12px #00ffe0;
  overflow: hidden;
}

#run-btn {
  margin: 1rem auto 2rem auto;
  display: block;
  background-color: #00ffe0;
  border: none;
  padding: 0.7rem 1.8rem;
  font-size: 1.3rem;
  font-weight: 700;
  color: #121212;
  border-radius: 6px;
  cursor: pointer;
  transition: background-color 0.25s ease;
  box-shadow: 0 5px 10px rgba(0, 255, 224, 0.6);
}

#run-btn:hover,
#run-btn:focus {
  background-color: #00d8cc;
  outline: none;
}

footer {
  text-align: center;
  padding: 1rem 0;
  background: #0f2027;
  color: #555;
  font-size: 0.8rem;
  user-select: none;
}