clear
unit 100.0
snap off
gridstyle grid off axes  off unit 1.0 1
style label  off coord  off filled  off font 14 color 0 0 0 fillcolor 128 128 128
let t=0.0
let base=[polygon [[-0.5, 2]  [-0.5, 2.1]  [0.5, 2.1]  [0.5, 2]  ] ]
Style base visible on unit 2 fillcolor 0 200 200 filled on 
let top=[halfplane [ [col 1 base]  [col 2 base] ] ]
Style top visible on fillcolor 128 64 0 filled on 
let A=[point [0.0, 2.0]]
Style A visible off font 12 
let P=[point [0.0, 6.0]]
Style P visible off 
let circle1=[circle [A P] ]
Style circle1 visible off 
let B=[pton circle1 0.85]
label B "Bob"
Style B visible on label on font 12 color 255 0 0 
let AB=[seg [A B] ]
Style AB visible off 
let Bob=[circle [B [translate B [0 .5] ]  ] ]
Style Bob visible on font 12 filled on 
let String=[seg [A [intersection AB Bob] ] ]
Style String visible on font 12 
program animatebob
AnimateBob
end
program AnimateBob
repeat 50 [ let t=t+1 let B=[pton circle1 0.75+0.1*[cos t*3.14/10]] paint pause 100]

end