This is my writeup for all reverse challenges. I hope you enjoy it and this is a link for all reverse challenges if you want to try to solve it https://drive.google.com/drive/folders/1yHtMB16MViUvYIjPTVwXhxNBsW0eE_YG?usp=sharing
We are given three files
Executing the given binary we will notice it’s a 2d shooter game where you have to avoid hitting the rocks within a certain time. If the time passes you will be moved to the next level, and from the description of the challenge we can know that to get the flag we should reach the end of the game
But here is the problem the first two levels are possible to win but the third is impossible
As the qualification the game is made by GameMaker engine but this time it used a different compiler so we can’t inspect the functions of the game using UndertaleModTool
There are two ways to solve this challenge in the CTF I used the unintended one Knowing that to make two objects hit each other in a game there must be something like a box for each object with a certain size and to know if they hit each other you can check if the two boxes intersect So I decided why not to try to make the size of these boxes zero so they never intersect
Opening the data.win file with UndertaleModTool then moving to sprites I made the size and the margin of the rocks and the player equal zero
Make sure to save the file sometimes it lags and doesn't save all the changes
And now we are Immune
Recording 2025-09-23 194229.mp4
And here is our flag
