Lets start
1. The challenge was that we had an old time's space invader game (like which i used to play in childhood xd ) After looking at the challenge the first thing i did was inspecting it (right clicke-> inspect element )2. There i found a link in the <iframe src="https://jef1056.github.io/" height="300" width="300"> ,guess what ? i clicked it xd and the game was there 3.So the next thing that poped into my mind was intercepting the link's request with burpsuite , there i found multiple request to server for files that were being used . From which this one seemed interesting to me https://jef1056.github.io/archive/game.arcd0 4.So i just used "wget https://jef1056.github.io/archive/game.arcd0 " to download this file and then just ran "strings game.arcd0 | tee game.txt" in linux (strings = to view the strings in a file | tee = to store the output of strings command in a txt file which will be easier to search)  and voila ther was the flag in my text file 
Flag :- rtcp{web_h^ck3r_0004212}