:root {
  --bg-color: #ffffff;
  --text-color: #111111;
  --card-bg: #e5e3e0;
  --card-text: #22211f;
  --btn-bg: #22211f;
  --btn-text: #ffffff;
  --btn-border: #ffffff;
  --modal-bg: #ffffff;
  --overlay-bg: rgba(0, 0, 0, 0.35);
  --input-border: #dddddd;
  --error-color: #d14b4b;
}

body.dark {
  --bg-color: #111111;
  --text-color: #ffffff;
  --card-bg: #1e1e1e;
  --card-text: #ffffff;
  --btn-bg: #ffffff;
  --btn-text: #111111;
  --btn-border: #111111;
  --modal-bg: #1e1e1e;
  --overlay-bg: rgba(0, 0, 0, 0.6);
  --input-border: #444444;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color 0.3s ease, color 0.3s ease;
}

.mode-toggle {
  position: fixed;
  top: 20px;
  right: 20px;
}

#toggle {
  display: none;
}

.toggle-label {
  width: 50px;
  height: 26px;
  background: #cccccc;
  border-radius: 20px;
  display: block;
  position: relative;
  cursor: pointer;
  transition: background 0.3s;
}

.toggle-label::after {
  content: "";
  width: 22px;
  height: 22px;
  background: #ffffff;
  border-radius: 50%;
  position: absolute;
  top: 2px;
  left: 2px;
  transition: transform 0.3s ease;
}

#toggle:checked + .toggle-label {
  background: #444444;
}

#toggle:checked + .toggle-label::after {
  transform: translateX(24px);
}

.title {
  font-size: 3rem;
  margin-top: 100px;
  text-align: center;
}

main {
  margin-top: 20px;
  padding: 40px;
  width: 900px;
  text-align: center;
  background-color: var(--card-bg);
  color: var(--card-text);
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  align-items: center;
  min-height: 300px;
}

.time {
  font-size: 4rem;
  margin-bottom: 30px;
  color: var(--card-text);
}

.buttons button,
.session-buttons button {
  background: var(--btn-bg);
  color: var(--btn-text);
  padding: 10px 20px;
  margin: 0 5px;
  border-radius: 10px;
  font-size: 1rem;
  cursor: pointer;
  border: 1px solid var(--btn-border);
  transition: all 0.3s ease;
}

.session-buttons {
  margin-top: 36px;
}

.buttons button:hover,
.session-buttons button:hover {
  background: var(--btn-text);
  color: var(--btn-bg);
  border-color: var(--btn-bg);
}

.modal {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--overlay-bg);
  backdrop-filter: blur(3px);
}

.modal-content {
  width: 600px;
  padding: 25px 30px;
  text-align: center;
  background: var(--modal-bg);
  color: var(--text-color);
  border-radius: 16px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
  animation: fadeIn 0.25s ease-in-out;
}

.modal-content h3 {
  margin-bottom: 15px;
  font-size: 1.2rem;
  font-weight: 600;
}

.modal-content input {
  width: 80%;
  padding: 10px;
  margin-bottom: 15px;
  font-size: 1rem;
  border-radius: 8px;
  border: 1px solid var(--input-border);
  background: transparent;
  color: var(--text-color);
  outline: none;
  transition: border 0.2s;
}

.modal-content input:focus {
  border-color: var(--text-color);
}

.modal-content button {
  padding: 8px 18px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.95rem;
  margin: 0 5px;
  border: 1px solid var(--btn-border);
  background: var(--btn-bg);
  color: var(--btn-text);
  transition: all 0.3s ease;
}

.modal-content button:hover {
  background: var(--btn-text);
  color: var(--btn-bg);
  border-color: var(--btn-bg);
}

.error {
  color: var(--error-color);
  font-size: 0.9rem;
  margin-bottom: 10px;
  height: 16px;
}

.alert {
  margin-bottom: 16px;
  font-size: small;
}

@media (max-width: 768px) {
  main {
    width: 85%;
    padding: 32px;
    min-height: auto;
    justify-content: center;
    align-items: center;
  }

  .title {
    font-size: 2.2rem;
    margin-top: 70px;
  }

  .buttons {
    margin-top: 10px;
  }

  .session-buttons {
    margin-top: 30px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    width: 100%;
  }

  .session-buttons button {
    width: 100%;
  }
}

@media (max-width: 480px) {
  main {
    width: 95%;
    padding: 24px;
    min-height: auto;
    justify-content: center;
    align-items: center;
  }

  .title {
    font-size: 1.8rem;
    margin-top: 50px;
  }

  .time {
    font-size: 2.8rem;
  }

  .buttons {
    display: flex;
    gap: 12px;
  }

  .session-buttons {
    margin-top: 24px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    width: 100%;
  }

  .session-buttons button {
    width: 100%;
    font-size: 0.95rem;
    padding: 10px;
  }
}