:root {
  --color-primary: #70c2bf;
  --color-primary-light: #c5e6e5;
  --color-background: #f3f3f3;
  --color-surface: #fbfbfb;
  --color-border: #a4a4a4;
  --color-text: #222;
  --color-text-light: rgba(0,0,0,0.75);
  
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 8px rgba(0,0,0,0.1);
  --shadow-inset: inset 0 2px 4px rgba(0,0,0,0.1);
}

html {
  box-sizing: border-box;
  font-size: 16px;
}

*, *:before, *:after {
  box-sizing: inherit;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.5;
  color: var(--color-text);
  position: relative;
  overflow: hidden;
}

.panel {
  background: var(--color-background);
  border-radius: 12px;
  box-shadow: var(--shadow-md);
  padding: var(--spacing-lg);
  width: min(90%, 600px);
  margin: var(--spacing-md);
}

.header {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.title {
  font-weight: 700;
  font-size: 1.75rem;
  line-height: 1.2;
}

.calculator {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

form {
  background-color: var(--color-surface);
  padding: var(--spacing-md);
  border-radius: 8px;
  border: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.input-group {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.spinner-btn {
  width: 28px;
  height: 28px;
  padding: 0;
  border: 2px solid var(--color-primary);
  border-radius: 6px;
  background: var(--color-surface);
  color: var(--color-primary);
  font-size: 1.25rem;
  line-height: 1;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

.spinner-btn:hover {
  background: var(--color-primary-light);
}

.spinner-btn:active {
  transform: scale(0.95);
}

input {
  width: 80px;
  padding: 0.5rem;
  border: 2px solid var(--color-primary);
  border-radius: 6px;
  font-size: 1rem;
  text-align: center;
  transition: all 0.2s ease;
  /* Hide default spinners */
  -moz-appearance: textfield;
}

/* Hide default spinners in WebKit browsers */
input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input:focus,
input:hover {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
  outline: none;
}

.result {
  background-color: var(--color-surface);
  padding: var(--spacing-md);
  border-radius: 8px;
  border: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: var(--spacing-sm);
  transition: all 0.3s ease;
}

.result.matching-dose {
  background-color: #e8f5e9;
  border-color: #4caf50;
  box-shadow: 0 0 8px rgba(76, 175, 80, 0.3);
}

#value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-primary);
}

.units-switch {
  position: relative;
  padding: 4px;
  background: #e1e1e1;
  border-radius: 20px;
  display: inline-flex;
  gap: 2px;
}

.units-btn {
  padding: 8px 16px;
  border-radius: 16px;
  border: none;
  background: transparent;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all 0.2s ease;
}

.units-btn.active {
  background-color: var(--color-primary-light);
  box-shadow: var(--shadow-inset);
}

.sub-text {
  font-size: 0.75rem;
  color: var(--color-text-light);
  text-align: center;
  margin-top: 4px;
}

.notes {
  background-color: #eee;
  padding: var(--spacing-md);
  border-radius: 8px;
  font-size: 0.875rem;
  line-height: 1.6;
  box-shadow: var(--shadow-inset);
}

/* Tablet Breakpoint */
@media screen and (max-width: 768px) {
  .panel {
    padding: var(--spacing-md);
  }
  
  .header {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .units-switch {
    justify-self: center;
  }
}

/* Mobile Breakpoint */
@media screen and (max-width: 480px) {
  html {
    font-size: 14px;
  }

  .panel {
    width: 100%;
    margin: 0;
    border-radius: 0;
    min-height: 100vh;
  }

  .calculator {
    grid-template-columns: 1fr;
  }

  form {
    gap: var(--spacing-md);
  }

  .input-group {
    width: 100%;
    justify-content: center;
  }

  input {
    width: 100%;
    max-width: 200px;
    padding: 0.75rem;
  }

  .spinner-btn {
    width: 36px;
    height: 36px;
  }

  .units-btn {
    padding: 10px 20px;
  }
}