:root {
  --input-border: #111827;        /* dark border for contrast */
  --input-bg: #ffffff;            /* white button surface */
  --input-text: #111827;          /* near-black text */
  --input-bg-hover: #111827;      /* dark background on hover */
  --input-text-hover: #ffffff;    /* white text on hover */
  --input-bg-disabled: #e5e7eb;   /* greyed-out background */
  --input-text-disabled: #9ca3af; /* muted text when disabled */
}

/* Page */

body {
  background: #ffffff;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: #111827;
}

/* Heading */

h1 {
  margin-top: 40px;
  margin-left: 20px;
  font-size: clamp(28px, 5vw, 40px);
  font-weight: 650;
}

/* Layout */

div {
  margin: 15px;
}

/* Player buttons (they are inputs of type="button") */

input[type="button"] {
  width: 100%;
  max-width: 220px;
  min-height: 80px;               /* good tap size on mobile */
  padding: 16px 20px;
  border-radius: 999px;           /* pill shape, modern */
  border: 2px solid var(--input-border);
  background-color: var(--input-bg);
  color: var(--input-text);
  font-size: 28px;
  font-weight: 600;
  text-align: center;
  box-shadow: 0 10px 24px rgba(15, 23, 42, 0.12);
  box-sizing: border-box;
  cursor: pointer;
  outline: none;
  transition:
    background-color 0.2s ease,
    color 0.2s ease,
    border-color 0.2s ease,
    box-shadow 0.2s ease,
    transform 0.1s ease;
}

/* Hover / focus only when enabled */

input[type="button"]:not(:disabled):hover,
input[type="button"]:not(:disabled):focus {
  background-color: var(--input-bg-hover);
  color: var(--input-text-hover);
  border-color: var(--input-bg-hover);
  box-shadow:
    0 0 0 3px rgba(17, 24, 39, 0.3),
    0 14px 30px rgba(15, 23, 42, 0.25);
  transform: translateY(-1px);
}

/* Visible focus ring for keyboard users */

input[type="button"]:focus-visible {
  outline: 3px solid #2563eb;
  outline-offset: 3px;
}

/* Disabled: greyed out, no hover cursor */

input[type="button"]:disabled {
  background-color: var(--input-bg-disabled);
  border-color: var(--input-bg-disabled);
  color: var(--input-text-disabled);
  box-shadow: none;
  cursor: not-allowed;
  transform: none;
}

/* Bootstrap grid tweaks on small screens */

.container {
  padding-top: 24px;
}

@media (min-width: 576px) {
  input[type="button"] {
    font-size: 32px;
    min-height: 96px;
  }
}