:root{--color-bg: #000000;--color-surface: #1a1a1a;--color-text: #f5f5f5;--color-accent: #4da3ff;--color-focus-ring: #ffd166;--color-value-high: #ff6b6b;--color-value-low: #5b9dff;--color-value-default: #f5f5f5}body{background:var(--color-bg);color:var(--color-text);font-family:arial,sans-serif;margin:0;min-height:100vh}#counter{background:var(--color-surface);color:var(--color-text);max-width:480px;margin:40px auto;padding:24px;border-radius:8px;text-align:center}#ttl{color:var(--color-text)}#d{font-size:40px;font-family:arial}button{border:none;border-radius:4px;cursor:pointer}button:focus-visible{outline:2px solid var(--color-focus-ring);outline-offset:2px}button[data-action=INCREMENT]{padding:10px;background:#4caf50;color:#fff}button[data-action=DECREMENT]{padding:10px;background:#ef5350;color:#fff}button[data-action=RESET]{padding:10px;background:#9e9e9e;color:#1a1a1a}button[data-action=ADD_FOUR]{padding:10px;background:#4da3ff;color:#fff}button[data-action=DOUBLE]{padding:10px;background:#b388ff;color:#1a1a1a}