Three activities, each one built into a specific block of a specific lesson. They run in any browser. Nothing to install, no account, no sound, no internet needed after the page loads.
For the parent. These replace a math or reading block, never the writing block — handwriting stays on paper, because grip endurance is one of his OT goals and typing skips it.
There is no timer in any of these, on purpose. Being rushed is one of his hard no's. The score is how many he got, never how fast. Nothing flashes red, nothing says "wrong," and there's no losing — a miss just says try again.
Cap it at one activity per lesson, around five minutes, so the shape of the lesson holds. Write his count on the tracking sheet — that's the number he's beating next time.