Press an aircraft, drag where you want it to go, let go. That is the
entire control scheme. Where you release decides what the order means —
the runway means land, an apron means park, and you can redraw any line
at any moment.
There is one runway. Everything arrives on it and everything leaves from
it, one aircraft at a time, and while somebody is rolling nobody else
can move. That single strip is the reason this job is hard.
Fuel only burns in the air. An aircraft parked on the ground is safe;
an aircraft circling overhead is on a clock. So the question is never
"where does this one go" — it is "who can afford to wait".
And they do not all arrive with the same tank. Some come in already
low. A jet that appeared thirty seconds after another one can still be
the one you have to take first, and the ring around it is the only place
that says so.
Land it, taxi it to the apron of its own colour, wait out the service,
send it home. Two bays per colour, so three of a kind means somebody
queues.
One runway. Everybody wants it. Fuel only burns while they are waiting.