On the left you can see all the forms and objects of the program individually.

So after that we can right-click the project and go to EntryPoint to find the starting point of the program or entryPoint,

and we see that the code for the main function is shown to us. We have to insert some text into the textbox and then hit the fire button to check the entered code,

then we'll see what happens after clicking the fire button and what code will execute. We can figure out what the secret is.

So, in order to find the code for the fire button, I look for an object on the left that has the click process.

 

As in the feature photo, the function related to the clicking process was the fire button. Just click on the method to show us the code.

 

Well here it is, the answer is so clear. As you can see in the code, the contents of the TextBox are compared to the RAINBOW statement and the rest is done. So we find out that the code is RAINBOW. Open the program and paste this code into TextBox. Well you see, the first cat with a rainbow gun got the wild cat up.