This is a little digital clock with an LED style display, using unicode characters.

edit: oh, sorry... the wiki doesn't allow unicode symbols apparently..

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package require Tk

pack [label .l -font {monospace 26} -background black -foreground red -relief ridge -borderwidth 16] -fill both -expand 1

proc every {ms script} {
 uplevel #0 $script
 after $ms [list every $ms $script]
}

every 16 {
 .l configure -text \
 [string map {0 %F0%9F%AF%B0 1 %F0%9F%AF%B1 2 %F0%9F%AF%B2 3 %F0%9F%AF%B3 4 %F0%9F%AF%B4 5 %F0%9F%AF%B5 6 %F0%9F%AF%B6 7 %F0%9F%AF%B7 8 %F0%9F%AF%B8 9 %F0%9F%AF%B9} \
  [string cat \
   [clock format [clock seconds] -format {%H:%M:%S.}] \
   [format {%02d } [expr {int([clock milliseconds]%1000/1000.0*100)}]]
  ] \
 ]
}
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