:root {
    --primary: #20c997;
    --teal-hover: #138d75;
    --navy: #001f3f;
    --dark-navy: #001737;
    --soft-gray: #f4f4f4;
    --white: #ffffff;
    --dark-bg: #1f1f1f;
    --dark-card: #2c2c2c;
    --light-text: #f0f0f0;
    --muted: #aaa;
    --gradient: linear-gradient(to right, #20c997, #138d75, #001f3f);
  }
  
  body {
    font-family: sans-serif;
    background: var(--soft-gray);
    margin: 0;
    color: #333;
    transition: background 0.3s, color 0.3s;
  }
  
  .dark-mode {
    background: var(--dark-bg);
    color: var(--light-text);
  }
  
  header {
    display: flex;
    justify-content: flex-end;
    padding: 1rem;
  }
  
  h1 {
    font-size: 1.8rem;
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-align: center;
    margin-bottom: 1rem;
  }
  
  main {
    text-align: center;
    padding: 1rem;
    max-width: 600px;
    margin: 0 auto;
  }
  
  .mode-buttons {
    margin-bottom: 1.5rem;
  }
  
  .mode-buttons button {
    margin: 0.3rem;
    padding: 0.6rem 1.2rem;
    border: none;
    background: var(--primary);
    color: white;
    border-radius: 8px;
    font-weight: bold;
    cursor: pointer;
    transition: 0.3s;
  }
  
  .mode-buttons button.active,
  .mode-buttons button:hover {
    background: var(--teal-hover);
  }
  
  .timer {
    font-size: 4rem;
    margin: 2rem 0;
  }
  
  .controls button {
    margin: 0.3rem;
    padding: 0.5rem 1rem;
    border: none;
    background: var(--navy);
    color: white;
    border-radius: 6px;
    cursor: pointer;
    transition: 0.3s;
  }
  
  .controls button:hover {
    background: var(--dark-navy);
  }
  
  #theme-toggle {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
  }
  
  .modal {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100vh;
    background: rgba(0,0,0,0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 10;
  }
  
  .modal-content {
    background: var(--white);
    padding: 1.5rem;
    border-radius: 10px;
    width: 90%;
    max-width: 400px;
    text-align: left;
  }
  
  .modal-content label {
    display: block;
    margin-bottom: 0.8rem;
  }
  
  .modal-buttons {
    text-align: right;
  }
  
  .modal-buttons button {
    margin-left: 0.5rem;
  }
  
  .hidden {
    display: none;
  }
  
  .dark-mode .modal-content {
    background: var(--dark-card);
    color: var(--light-text);
  }
  
  input[type="number"] {
    width: 60px;
    padding: 0.2rem;
    margin-left: 0.5rem;
  }