update - I have now added colors and to double the size press right mouseclick and to go back down it is shift.
Enjoy
do
a#=rnd(15)
b#=rnd(15)
q#=rnd(15)
w#=rnd(15)
e#=rnd(15)
aa#=rnd(20)
ba#=rnd(20)
qa#=rnd(20)
wa#=rnd(20)
ea#=rnd(20)
if inkey$()="r" then ink rgb(255,0,0),0
if inkey$()="g" then ink rgb(0,255,0),0
if inkey$()="b" then ink rgb(0,0,255),0
if inkey$()="w" then ink rgb(255,255,255),0
if mouseclick()=1
dot mousex()+a#,mousey()
dot mousex(),mousey()+q#
dot mousex()+a#,mousey()+e#
dot mousex()+w#,mousey()
dot mousex(),mousey()+b#
dot mousex()+a#,mousey()+e#
if m#=1
dot mousex()+aa#,mousey()
dot mousex(),mousey()+qa#
dot mousex()+aa#,mousey()+ea#
dot mousex()+wa#,mousey()
dot mousex(),mousey()+ba#
dot mousex()+aa#,mousey()+ea#
endif
endif
if mouseclick()=2
size#=size#+1
wait 150
endif
if shiftkey()=1 then size#=0 : m#=0
if size#=1 then m#=1
loop