ATC is a simple air traffic control emulator.

26 Airplanes take off at airports or come in at one of the 10 fixes, and then
land at airports or exit at one of the ten fixes.   The game is over when all
26 airplanes have exited the board at the proper place, or when one of several
failures occur such as planes colliding, flyover of airports at zero altitude without
landing, or exiting the board at the wrong location.

To play the game select 'start' from the file menu.   IT will ask for a time,
enter a time between 16 and 100 minutes.   Higher times make the game easier
as the airplanes will be more spread out; lower times make it harder as more
airplanes have to be handled at once.

At the beginning of each minute, one or more airplanes may be scheduled for arrival.
The airplanes coming in in the next minute will be described to the right of the board.
For example:

YJN 9 5 TO $ +

A jet named Y is heading north from fix 5 at altitude 9 and will land at airport $, 
and has more than ten minutes of fuel left.

Airplanes are named with a letter of the English Alphabet.

There are two types of planes, Jets ('J') and Props ('P').   Jets move twice as fast
as props.  Jets move 4 times per minute; props twice per minute.

The fixes are numbered from to 9.   The airports are named '$' and '%'.   Additionally,
there are two navaids, one for each airport, and these are each denoted with a '*'.

To command a plane, right click on it and a menu will appear.  The top of the menu
will show the plane's stats as described above.   You can rotate left or right, set the
altitude, command the plane to circle around a navaid, or set the cleared to land state.

To change directions, rotate left or right.   There are four rotate commands of each type;
labeled from 1 to 4.   When set to 1 the plane will turn left or right on the next move
then continue on the same heading.   When set to a value greater than one, the plane will
turn left or right for each of the next n moves, where n is the value.   At the end of
all the turns, the plane will continue in the final direction.

The airplanes may have an altitude from 0 to 9.   To land at an airport, set the altitude
to 0 then fly into the airport from the direction of its navaid.   Flying over an
airport at altitude zero when you aren't supposed to land at it or from any other
direction will end the game with an error.

To exit at a fix, set the altitude to 5 or greater, then point the plane at a ninety 
degree angle to the fix and let it fly off the board.  Exiting at two low of an altitude
or at the wrong direction or at any other position other than the intended fix will
end the game with an error.

You can do two things with navaids: circle around them and use them in the 'clear to land'
scenario.  When you select circle navaid the plane will keep a similar distance around the
closest navaid, to what it already has.   When you select clear to land, flying over the
navaid from any direction will cause the plane to set its heading for the navaid's airport
and set the altitude to zero in preparation for landing.

If a plane runs out of fuel, or if two planes at the same altitude come to a distance
of 3 or less from each other, the game will end with an error.
