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I dug around a bit and did not find a simple and clear implementation of countdown stopwatch in Mathematica. I am looking for a function that takes as an input a certain integer and then counts down by 1 every second till 0 is reached. I think it could be an important part for some examples. Kernel or Front End implementations are both acceptable. Here is my take on it:

timer[s_] := Module[{x = AbsoluteTime[], y = AbsoluteTime[]}, 
              RunScheduledTask[y = AbsoluteTime[], {1, s}];
              Dynamic[s - Floor[y - x]]]

It's a bit hacky but works ;-) I have seen the following questions already:

but I do not think they do what I was looking for. They either run time forward, are too complex, or something else. Did I miss anything? Does anyone have better ideas?

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up vote 8 down vote accepted

What about

timer[s_] := Dynamic[s - Clock[{0, s, 1}, s, 1]]
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+1 Very nice ;) I wonder if there are any other solutions. – Vitaliy Kaurov Jul 22 '12 at 2:32
@Rojo Anolther question, but... is it possible to forse Mathematica to play a sound when 0 is reached? – Alexey Popkov Jul 22 '12 at 6:36
@AlexeyPopkov it seems like Clock updates one extra time when it stops. But we can always do timer[s_] := DynamicModule[{guard = True}, Dynamic[ If[guard && # === 0, Beep[]; guard = False; #, #] &[ s - Clock[{0, s, 1}, s, 1]]]] – Rojo Jul 22 '12 at 12:09

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