I can understand your title pretty well; it's because of the sounds the heart makes when it beats, right? But if you want to make it sound like the heart is thumping hard and crazily (like Youngjae's is in the story), then maybe badum badum might be better. Though Pit-A-Pat is fine as well, except it seems a bit...I'm not sure, but cringey? However, because I don't really prefer reading fluff stories, it might be the case, so you can ignore this point. 

Your description doesn't have really any problems with it, but it somehow gives me a wrong sort of impression. While the story is about unrequited love etc etc, your description gives off a feeling of Youngjae being a lovesick teenager who seems a bit too desperate and constantly daydreaming about his crush. This part is in fact true, and is what is about your story, but you can add a bit of an involvement about Daehyun. You can mention Youngjae sneaking glances at his crush and so on. Just a tiny detail, but it would've been more convincing. 

As for your foreword, there aren't any problems about it so it's fine. 

Everything's fine and well. I really like the detail of the heartbeat line (or whatever it's called) on the top of your chapter. 

You've mentioned that your story is based on 'In A Heartbeat', so I went and watched the video. So, first of all, I'd like to say that the details of your story and the video quite matched, and you've brought out the idea of the video nicely, so kudos to you about that. 

However, there is something lacking about your story which makes the video better. First of all, your emotions. It just doesn't seem convincing enough. I'll go over the details in the characterisation section, but to me, none of the characters are real, nor are they relatable. Yes, you may argue that characters in a story doesn't exist in real life. But see, well-written stories more often than not can cause a character to come to life in front of your own eyes. However, to me, the Youngjae and Daehyun in your story are mere characters. And nothing more. It's true that one can relate to them when one is desperately lovesick or has a huge crush on someone else, but at least, to me it doesn't seem convincing. (then again there's the part of which I'm not really a cheerful person that comes to notice - ) 

Anyways. 

There are also some plot holes which I'd like to mention. You said that the boys are both in highschool? Somehow neither of them behave like students in highschool. To me, the sort of behavior the two displays can only be seen in America (you know, the cliche highschool dramas which are often about blondes etc etc). It wasn't just their emotions and actions (which can be explained), but the fact that Youngjae doesn't know about the reason of his heart beating that quickly. I know that potraying them as middle-school age would be quite weird as they're adults, but like, I can't imagine any highschooler not knowing or imagine that. 

You also changed the detail of him hiding in the bushes instead of the trash can, which I admit i greatly appreciate. And....okay. The detail which I hated the most. Daehyun, was said to not know who Youngjae was (or at least there was no indication of it). No normal person would've kissed after seconds of meeting them, and especially after a fiasco like this. If Daehyun is trying to comfort Youngjae, he could've easily just hugged him or maybe the two of them could've sat under the tree holding hands like what happened in the video - anything but taking the ripening relationship so quickly. It's not realistic at all, and if this did happen in real life I'd be shocked beyond repair. 

And that's about it for the plot. Your flow is alright though; not too quick or not too slow. 

The details, overall, are fine. You give enough to let the readers know what is happening where and when, but there could be more that can be added, such as Daehyun's reactions and dialogues etc etc. 

I think I mentioned it in the plot part, but the flow of the story was alright, not too quick nor slow. Still, I would like to see more character development on Daehyun because he just seems like a surreal character. 

So first of all I really like the idea of incorporating the video's theme and idea in your story, but somehow you couldn't bring out the underlying message. Still, I quite like the whole idea of the story.

However, there are many places which you can improve on and which I wish to see improvement on, especially Daehyun. I also didn't really like that everything seemed too perfect - and your choice of words and writing style a little dragging. 

Daejae is one of my favourite OTPs, and I'm glad that you pulled off Youngjae's dorky nature ^^ 

Overall, this was quite a nice read, but again there are scenes where everything seemed a bit too perfect and plain. I hope I don't sound too harsh throughout the review > < 

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