BalloonTD, a remake of a series of popular flash games: Bloons Tower Defence.
LibGDX actually uses Gradle to manage project. Although there are gradlew and gradlew.bat came with LibGDX, I don't really know what OS you are running on. Thus make run will run a premade JAR file.
If you want to use Gradle, use make run_gradle_linux or make run_gradle_windows. Note that this will install gradle in your home directory. More information about this at https://github.com/libgdx/libgdx-gradle-template
Most of the source code is in core/src/.... Platform-dependent code is in directories like desktop/, html/, etc.
For a more detailed introduction and explanation to this project, please refer to report.pdf.