This is the only screen in the set designed around a physical constraint rather than a taste: eleven in the morning, outdoors, one hand on the phone, sometimes a work glove.
Near-black and a saturated amber, because that pair survives direct sun on a cheap LCD at half brightness. There are no mid-greys anywhere in this application. In sunlight a mid-grey label is not there.
The usual minimum is written for somebody sitting indoors. Every
tappable thing here is 64 px or larger and the
actions sit at the bottom, because the top of a six-inch phone cannot
be reached by the hand holding it.
Every mark is written on the phone with its own sequence number and the header says how many are waiting, in words. The count goes down on the way home. Nothing waits for a tower.
A photograph, a location and a time, stamped together at the moment of marking and not editable afterwards. That is not surveillance of the supervisor. It is what lets a supervisor defend the roll when somebody queries it eight months later.
The same job card marked present at two worksites on one day, and a mark taken well outside the site boundary. Both are arithmetic. In both cases the software refuses to decide: it shows the supervisor what it found and makes them write down what happened, and that sentence goes on the record with the mark.
Tap any name. Three of the thirty-four are already marked present somewhere else today, and several are standing outside the boundary. Those are the ones that will argue with you.