added playground project and made (again) the common.cmake behave when included multiple times
diff --git a/scripts/playground/main.cpp b/scripts/playground/main.cpp
new file mode 100644
index 0000000..5da4c16
--- /dev/null
+++ b/scripts/playground/main.cpp
@@ -0,0 +1,30 @@
+#include "parts/doctest_impl.h"
+
+int main(int argc, char** argv) {
+    doctest::Context context;
+
+    // !!! THIS IS JUST AN EXAMPLE SHOWING HOW DEFAULTS/OVERRIDES ARE SET !!!
+
+    // defaults
+    context.addFilter("test-case-exclude", "*math*"); // exclude test cases with "math" in the name
+    context.setOption("no-breaks", true); // don't break in the debugger when assertions fail
+
+    context.applyCommandLine(argc, argv);
+
+    // overrides
+    context.setOption("order-by", "name"); // sort the test cases by their name
+
+    int res = context.run(); // run
+
+    if(context.shouldExit()) // important - query flags (and --exit) rely on the user doing this
+        return res;          // propagate the result of the tests
+
+    int client_stuff_return_code = 0;
+    // your program - if the testing framework is integrated in your production code
+
+#ifdef WITH_PAUSE
+    system("pause");
+#endif // WITH_PAUSE
+
+    return res + client_stuff_return_code; // the result from doctest is propagated here as well
+}