How many buttons can this person actually hit, at what size, and where on the screen? It is the question that comes before every page set, and the usual way to answer it is to hand somebody a device and watch. Grid Fit is that — except the grid is a game board, so the player is playing rather than being tested.

Whack-a-Mole is the one that does the real work. A mole pops up in one button at a time; bonk it and it comes up somewhere new. It never comes up where it just was, and it always chooses a button it has visited least — so a session sweeps the whole grid instead of settling in whichever corner is easiest to reach. That is the difference between a game on a grid and a grid trial: it is the far corner you need to see attempted, and free play will never send anyone there. Pop Them All puts a balloon on every button and asks for the board to be cleared, which guarantees the same coverage at the player's own pace. Free Play is there for the session before either of those matter: every button does something, every time, with no goal and no end.

The mole waits as long as this player needs. Its patience is a setting — and a ceiling rather than a promise. With switch scanning it always waits, because a mole on a timer can duck before the sweep has even reached it, which makes the game quietly unwinnable. With eye-gaze it never gets less than one full dwell plus the time to look across. The app says so on screen when it has done this, so nobody is left wondering why Quick is not behaving like Quick.

Setting it up is one panel, in four numbered steps, with a picture of the grid beside them that changes as you press. Pick the game, pick how many buttons — the common grids are drawn rather than named, so 2 x 4 looks like 2 x 4 — then say where they sit. Whole screen, top half, bottom half, left half, right half or middleare one press each, and they are where most sessions start and finish.

Fitting a keyguard is a physical job, so the controls are physical. Lay the guard on the glass and adjust until every button comes up inside an opening: rows and columns from 1 x 2 to 8 x 10, width and height to pull the grid in off the edges of the display, and gap for the rail between one button and the next. Then move the whole grid higher or lower, left or right — because a mounted device, a low head position, or a guard whose openings do not start at the top all mean centred is the wrong answer. Quick steps get the grid close; then Fine tune switches to sub-percent size and position changes, plus half-pixel gap changes, so each edge can disappear cleanly behind the guard instead of stopping a few pixels short. Exact horizontal and vertical values stay visible while you adjust. The same controls are also on a small panel that floats over the grid itself, for the half of the job that has to be done against the real thing at its real size. And when the grid already fills the screen there is nowhere to move it to, so the arrows say so and switch themselves off rather than answering a press with nothing.

Full-screen fit is what makes that reach the whole screen. The app's own header, status row and tool bar leave the play area a little over half the height of the display, and a keyguard's openings run right to the top and bottom edges of the glass. Full-screen fit stands all of that down — including the margin the app normally keeps clear at the edges — so the grid can sit flush in any corner, or fill the display completely. It is a switch on the setup panel rather than a door out of it, so the picture beside it changes shape the moment it goes on.

The app reports how big each button actually is, in pixels, and says so plainly when a grid has dropped its targets below the 44-pixel minimum. And it tracks coverage rather than presses: a player who hits one corner twelve times has not shown you a grid that fits. A score bar across the top can be switched on — it keeps the score, and it takes its height out of the grid, exactly like the message window on a real page set does.

Everything works with touch, a single switch, two switches, or eye-gaze dwell. Each row is its own scan group, so group scanning becomes ordinary row-column scanning here; item scanning gives a linear sweep of every button. Scan speed, dwell time, target size and spoken feedback are all in the app's Settings panel, and the grid you settle on is saved on the device with the rest of that player's setup.