:root {
    --primary-color: #2c3e50;
    --secondary-color: #1a252f;
    --accent-color: #3498db;
    --button-bg-color: #2980b9;
    --button-hover-bg-color: #1d6f8c;
    --input-bg-color: #ecf0f1;
  }

  body, html {
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    height: 100%;
    background-color: #ecf0f1;
  }

  #login-screen {
    position: fixed;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #f0f0f0;
  }

  #login-box {
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    width: 300px;
    text-align: center;
  }

  #login-box input {
    width: 100%;
    padding: 10px;
    margin: 10px 0;
    border-radius: 4px;
    border: 1px solid #ccc;
    box-sizing: border-box;
    background-color: var(--input-bg-color);
  }

  #login-box button {
    background-color: var(--button-bg-color);
    color: white;
    padding: 10px;
    border-radius: 4px;
    width: 100%;
    cursor: pointer;
    border: none;
    transition: background 0.3s ease;
  }

  #login-box button:hover {
    background-color: var(--button-hover-bg-color);
  }

  #app {
    display: none;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
  }

  .header {
    background: var(--primary-color);
    color: white;
    padding: 6px 15px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 0.9rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
  }

  .header select {
    padding: 5px;
    border-radius: 4px;
    border: none;
    background-color: var(--input-bg-color);
  }

  .main {
    display: flex;
    flex-grow: 1;
  }

  .content {
    flex-grow: 1;
    padding: 20px;
    overflow-y: auto;
  }

  .hidden {
    display: none;
  }

  .connect {
    animation: connect 3s ease-in-out infinite;
  }
  @keyframes connect {
    0%, 100% { stroke-dashoffset: 0; }
    50% { stroke-dashoffset: -8; }
  }