Initial Cross Platform Work

include/pd/core/tween.hpp

@@ -23,7 +23,11 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
  */
 
-#include <pd/core/vec.hpp>
+#include <pd/core/common.hpp>
+
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
 
 namespace PD {
 /**