Extreme Concentration Trainer is a Bourdon-style attention drill. A highlight moves through a field of letters. You mark assigned symbols with 1, 2, and 3 (or 1–4 / 1–5 in Settings), and press Space to skip everything else. Correct marks light up green. Missed targets light up yellow. Wrong marks light up red. Pace is yours — Space sets the tempo. Customize letter size, spacing, background color, and capitals (a–z or A–Z). Scores stay on this device. No account. Works on iPhone, iPad, and Mac.
