Code Blocks are often adding "default files" to your project when you create a new project. Predefined main programs, headers and so on. Perhaps, some people like it. As I have just checked, you have become a victim of such behaviour :mrgreen:
Check file tree and delete all unwanted files (files you have not written) from it. Try compiling again. Luckily, wxWidgets project has an option "create empty project" (a checkbox) while creating a project, which cause no additional files in your newly created project. You will start an empty project with no files and your first action will be adding a new file to the project.
