* {
  box-sizing: border-box;
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #ffffff;           /* pure white - best for most e-ink */
  color: #000000;                /* pure black */
  margin: 0;
  padding: 1.5rem 1rem;
  line-height: 1.45;
  font-size: 18px;               /* larger base size - e-ink benefits from bigger text */
}

.container {
  background: #ffffff;
  border: 2px solid #000000;     /* visible, sharp border */
  border-radius: 0;              /* no rounding - reduces ghosting artifacts */
  padding: 2rem;
  max-width: 100%;
  margin: 0 auto;
}

h1 {
  font-size: 2.4rem;
  margin: 0 0 1.8rem;
  text-align: center;
  color: #000000;
  border-bottom: 3px solid #000;
  padding-bottom: 0.6rem;
}

.input-group {
  margin: 1.8rem 0;
}

label {
  display: block;
  margin-bottom: 0.6rem;
  font-size: 1.1rem;
  font-weight: bold;
}

input {
  width: 100%;
  padding: 0.9rem;
  font-size: 1.1rem;
  border: 2px solid #000000;
  border-radius: 0;
  background: #ffffff;
  color: #000000;
}

input:focus {
  outline: 3px solid #444444;
  outline-offset: -2px;
}

.buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin: 2rem 0;
}

button {
  padding: 1rem 2rem;
  font-size: 1.2rem;
  font-weight: bold;
  border: 3px solid #000000;
  background: #ffffff;
  color: #000000;
  border-radius: 0;
  cursor: pointer;
  min-width: 140px;
}

/* Different button styles using patterns instead of colors */
button.btn-primary {
  border-width: 4px;
  border-style: solid;
}

button.btn-success {
  border-style: double;
  border-width: 5px;
}

button.btn-danger {
  border-style: dashed;
  border-width: 4px;
}

button.btn-info {
  border-style: dotted;
  border-width: 5px;
}

/* Hover/focus - minimal for e-ink (many don't have hover) */
button:active,
button:focus {
  background: #e0e0e0;
  outline: 4px solid #000;
  outline-offset: -4px;
}

#output {
  margin-top: 2rem;
  padding: 1.5rem;
  border: 2px solid #000000;
  min-height: 120px;
  background: #f8f8f8;          /* very light gray - still high contrast */
  font-size: 1.1rem;
  white-space: pre-wrap;
  line-height: 1.6;
}