Fitts's law
Bigger and closer targets are faster to hit. The math behind large buttons, edge menus, and 44px tap targets.
See it
What it is
Paul Fitts, 1954: the time to hit a target grows with distance and shrinks with target size, roughly MT = a + b * log2(2D / W). Two knobs, then: how far the pointer travels, and how big the thing is when it gets there. Screen edges get a bonus, because the cursor stops dead at them, which makes an edge target effectively infinitely wide. That is why the macOS menu bar sits flush against the top and why the Windows Start button lives in a corner.
The numbers you will actually be held to: 44 by 44 pt in Apple's Human Interface Guidelines, 48 by 48 dp in Material, and 24 by 24 CSS pixels in WCAG 2.2 Target Size (Minimum), which carries real exceptions for sufficiently spaced targets, inline targets inside a sentence, controls the user agent draws, and cases where the size is essential to the information. Grow the hit area with padding or an invisible expanded region rather than inflating the visual box, put the primary action where the cursor already is (next to the field just filled, not across the dialog), and handle destructive actions by separation rather than by shrinking: park them away from the primary action, style them quietly, and still give them a hit area that meets the guidance. A 4-pixel Delete button is an accessibility bug wearing a safety costume, and it punishes exactly the people most likely to misfire.
Gotcha: it gets quoted as 'bigger is always better', which is wrong past a certain size. The gain is logarithmic, so doubling a button that is already comfortable buys almost nothing while pushing everything else further away and adding travel. It also models pointing devices; on touch, finger occlusion and grip reach matter more, and for keyboard users the law does not apply at all.
Ask AI for it
Audit and fix the controls in this UI against Fitts's law. Give every interactive element a hit area of at least 44 by 44 px, adding padding or an invisible expanded touch region instead of enlarging the visual shape. Move the primary action close to where the pointer already is at the end of the task, make it the largest target in its group, and place destructive actions well away from it with no adjacency. Keep those destructive controls at the same 44 by 44 px minimum while making them visually quieter (secondary or text styling, never a smaller target), since shrinking the hit area to prevent mistakes only creates different ones. Anchor persistent global controls to a screen edge or corner so the pointer can slam into them, and never put a small icon-only button inside a dense row without spacing around it.