Could not find property ‘classesDir’ on source set main

[ramAdam]

I am using Gradle 5.1.1, in case you get "classdir" error, see fix 1 below

Fix #1:
desktop build.gradle:
line 27,
change this:
from files(sourceSets.main.output.classesDir)
to:
from files(sourceSets.main.output.classesDirs)

Fix #2:
uncomment line 60 in main build.gradle
compile "com.underwaterapps.overlap2druntime:overlap2d-runtime-libgdx:0.1.1-SNAPSHOT"

and change it to
compile "com.underwaterapps.overlap2druntime:overlap2d-runtime-libgdx:0.1.2-SNAPSHOT"

run:
gradle desktop:run