:root {
  --color-bg: #0f0f0f;
  --color-surface: #1a1a1a;
  --color-primary: #4f9cf9;
  --color-secondary: #3a3a3a;
  --color-text: #e8e8e8;
  --color-muted: #666;
  --color-danger: #e05c5c;

  --font-timer: monospace;
  --size-timer: clamp(4rem, 18vw, 7rem);

  --radius-container: 1rem;
  --radius-btn: 0.5rem;
  --transition: 160ms ease;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 1rem;
  font-family: 'Segoe UI', system-ui, sans-serif;
  font-size: 1rem;
  color: var(--color-text);
  background-color: var(--color-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

.timer-container {
  width: 100%;
  max-width: 600px;
  background-color: var(--color-surface);
  border-radius: var(--radius-container);
  padding: 3rem 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
}

.timer-display {
  font-family: var(--font-timer);
  font-size: var(--size-timer);
  font-weight: 600;
  letter-spacing: 0.05em;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
}

.timer-separator {
  color: var(--color-muted);
  opacity: 0.6;
}

.timer-input {
  background-color: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  text-align: center;
  font-family: inherit;
  font-size: inherit;
  font-weight: inherit;
  color: inherit;
  cursor: pointer;
  padding: 0.25em 0;
  transition: border-color var(--transition), opacity var(--transition);
  width: 1.8em;
}

.timer-input:focus {
  outline: none;
  border-bottom-color: var(--color-primary);
  cursor: text;
}

.timer-input:disabled {
  opacity: 0.6;
  cursor: default;
}

.timer-controls {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  padding: 0.75rem 2rem;
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-btn);
  cursor: pointer;
  transition: all var(--transition);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.btn--primary {
  background-color: var(--color-primary);
  color: #000;
}

.btn--primary:hover:not(:disabled) {
  background-color: #5ba8ff;
  transform: translateY(-2px);
}

.btn--primary:active:not(:disabled) {
  transform: translateY(0);
}

.btn--primary:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn--secondary {
  background-color: var(--color-secondary);
  color: var(--color-text);
}

.btn--secondary:hover:not(:disabled) {
  background-color: #4a4a4a;
  transform: translateY(-2px);
}

.btn--secondary:active:not(:disabled) {
  transform: translateY(0);
}

.btn--secondary:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.timer-container.is-finished .timer-display {
  animation: pulse 0.6s ease infinite alternate;
  color: var(--color-danger);
}

@keyframes pulse {
  from {
    opacity: 1;
  }
  to {
    opacity: 0.4;
  }
}

@media (min-width: 480px) {
  .timer-container {
    padding: 4rem 3rem;
  }

  .btn {
    padding: 1rem 2.5rem;
    font-size: 1.1rem;
  }
}