fatcat

@echo off & setlocal enabledelayedexpansion
set /a sz=28, wid=2*sz+1, Cols=2*wid, iMax=wid*wid
for /l %%i in (1 1 !iMax!) do set "scr=　!scr!"
color 0a & mode con cols=!Cols! lines=!wid!
set /a xC=25, yC=30, r=15 & rem 指定圆心及半径
for /l %%n in (1 1 5) do (
  call :mpc
  set /a "xC=!random!%%wid, yC=!random!%%wid, r=!random!%%(wid*2/3-10)+10"
)
echo !scr!& pause & exit /b

:mpc rem midpoint circle algorithm 中点画圆算法
set /a x=0, y=r, d=-r
for /l %%i in (1 1 999) do (
  for %%# in (1 2) do (
    for %%x in (-!x! !x!) do for %%y in (-!y! !y!) do (
      set /a xd=%%x+xC, yd=%%y+yC, "inScr=(xd-1^xd-wid)&(yd-1^yd-wid)
      if !inScr! lss 0 (
        set /a ind=xd+yd*wid+1, lenL=ind-1, lenR=iMax-ind
        for /f "tokens=1,2,3" %%a in ("!lenL! !ind! !lenR!") do (set scr=!scr:~0,%%a!·!scr:~%%b,%%c!)
      )
    )
    set tmp=!x!&set x=!y!& set y=!tmp!
  )
  set /a x+=1, d+=1+(x"<<1)
  if !d! geq 0 set /a y-=1, d-=y"<<1
  if !y! lss !x! exit /b
)
exit /b
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