Greetings.

Recently I have been working on a project for a class. Within the project I am attempting to display multiple circles constantly increasing in size as a For loop progresses. I have no problem increasing the size of the circles, nor displaying the circles, but the circles are constantly being over written by the next circle. I have been attempting to find a way to combine all of the circles into one graph, and also combine each circle into it's own graph (for individual use). This is the code I have written so far (there will also be an attatched copy).

xSt[] = 0; (* x starting position *)

ySt[] = 0; (*y starting position *)

years = 0; (* The years that pass *)

endTime = 100; (* Amount of years until the end of time *)

probLife = 0; (* The probability that life will sprout up *)

nLife = 0; (* Amount of Circles of Life; and designation number *)

circleLife[] = 0; (* Circle of Life *)

rMulti = 0 ; (* Growth multiplier *)

rBase = 0; (* Base growth rate *)

rGrowth[] = 0; (* Rate of Growth for each CoL *)

orgGrowth[] =

0; (* Used to keep track of original growth rate assigned to \

specific life form *)

ContourPlot[x y, {x, -1, 1}, {y, -1, 1},

PlotRange -> {{-100, 100}, {-100, 100}},

PlotLabel -> Dynamic["Year = " <> ToString[years]],

Epilog -> Dynamic[plot[[1]]]]

For[years = 1, years < endTime,

probLife = RandomInteger[{1, 10}];

(* The following If function checks if there are any circles of \

life and if there is, begins updating them,

as if the life form is expanding radially *)

If[nLife > 0,

For[n = 1, n <= nLife,

n++,

rGrowth[n] = rGrowth[n] + orgGrowth[n];

plot =

ContourPlot[((a - xSt[n])^2 + (b - ySt[n])^2 ==

rGrowth[n]^2), {a, -100 \[Pi], 100 \[Pi]}, {b, -100 \[Pi],

100 \[Pi]},

PlotRange -> {{-100, 100}, {-100, 100}}];

(* Pause[0.1] *)](* End For n *)

]; (* End If nLife *)

(* The following If function checks if the probability of life \

forming is true and if so creates a new form of life at a random \

point on the plot and the size and growth rate of that life form *)

If[probLife == 1,

{nLife = nLife + 1;

xSt[nLife] = RandomReal[{-100, 100}];

ySt[nLife] = RandomReal[{-100, 100}];

rMulti = RandomReal[{.01, .1}];

rBase = RandomReal[{1, 10}];

rGrowth[nLife] = (rMulti rBase);

orgGrowth[nLife] = (rMulti rBase);

plot =

ContourPlot[((a - xSt[nLife])^2 + (b - ySt[nLife])^2 ==

rGrowth[nLife]^2), {a, -100 \[Pi],

100 \[Pi]}, {b, -100 \[Pi], 100 \[Pi]},

PlotRange -> {{-100, 100}, {-100, 100}}]};

]; probLife = 0;(* End If probLife *)

(* Pause[0.1]; *)

years++;

] ;(* End For years*)

Also, while attempting a variety of different methods and approaches, I receive this error message

"An improperly formatted option head (Graphics) was encountered while reading a Graphics. The head of the option must be Rule or RuleDelayed."

But I do not know exactly what it means, and my searches for an answer to this online has been fruitless.

Please help me Mathematica Community, you're my ony hope.

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