TRACKER is an equation-graphing game. Graphs are hidden on a 
coordinate grid. You enter their equations to "track" them.

You get clues to the graphs' locations by using "probe shots." 
Probe shots are equations of horizontal or vertical lines. 

When a probe shot crosses a hidden graph, it marks that point 
with an X or an 0.

The types of graphs you choose include the following:
     .straight line
     .parabola
     .circle
     .ellipse
     .hyperbola (two kinds)

There are three levels of difficulty:
Practice is a good place to start. You choose the type of hidden graph. 
Either one or two graphs are hidden on the grid. No score is kept.
Novice Game allows you to choose two types of graphs. Three graphs are 
hidden on the grid (two of one type and one of the other). 
One type of graph is marked by X's and the other by O's when hit by a 
probe. When you have enough clues, you send a tracker along the graph 
by entering its equation. Expert Game chooses the two types of graphs 
at random, so you'll need to discover what type they are as well as 
where they are! You choose how many graphs are hidden, three through six.

Scoring
You score points for correctly tracking each graph:
       Graph Type         Points Scored
       straight line      30 points 
       parabola           35 points 
       circle             40 points 
       ellipse            45 points         
       hyperbola          50 points

You lose points for each probe and for incorrect trackers:
        Action               Points Lost
        first probe          1 point
        second probe         2 points
        third probe          3 points
        ..and so forth
        incorrect tracker    10 points