message: Include trailing slash as part of folder variables
  This more clearly represents a folder name value.
diff: # Source http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/
  -SRCDIR := src
  -BUILDDIR := .build
  -OBJDIR := $(BUILDDIR)/obj
  +SRCDIR := src/
  +BUILDDIR := .build/
  +OBJDIR := $(BUILDDIR)obj/
  EXE := OPHD
  -NAS2DDIR := nas2d-core
  -NAS2DINCLUDEDIR := $(NAS2DDIR)/include
  -NAS2DLIBDIR := $(NAS2DDIR)/lib
  -NAS2DLIB := $(NAS2DLIBDIR)/libnas2d.a
  +NAS2DDIR := nas2d-core/
  +NAS2DINCLUDEDIR := $(NAS2DDIR)include/
  +NAS2DLIBDIR := $(NAS2DDIR)lib/
  +NAS2DLIB := $(NAS2DLIBDIR)libnas2d.a
  CFLAGS := -std=c++17 -g -Wall -Wno-unknown-pragmas -I$(NAS2DINCLUDEDIR) $(shell sdl2-config --cflags)
  LDFLAGS := -lstdc++ -lm -L$(NAS2DLIBDIR) -lnas2d \
  $(shell sdl2-config --libs) -lSDL2 -lSDL2_image -lSDL2_mixer -lSDL2_ttf \
  -lphysfs -lGL -lGLEW
  -DEPFLAGS = -MT $@ -MMD -MP -MF $(OBJDIR)/$*.Td
  +DEPFLAGS = -MT $@ -MMD -MP -MF $(OBJDIR)$*.Td
  COMPILE.cpp = $(CXX) $(DEPFLAGS) $(CFLAGS) $(TARGET_ARCH) -c
  -POSTCOMPILE = @mv -f $(OBJDIR)/$*.Td $(OBJDIR)/$*.d && touch $@
  +POSTCOMPILE = @mv -f $(OBJDIR)$*.Td $(OBJDIR)$*.d && touch $@
  SRCS := $(shell find $(SRCDIR) -name '*.cpp')
  -OBJS := $(patsubst $(SRCDIR)/%.cpp,$(OBJDIR)/%.o,$(SRCS))
  +OBJS := $(patsubst $(SRCDIR)%.cpp,$(OBJDIR)%.o,$(SRCS))
  FOLDERS := $(sort $(dir $(SRCS)))
  .PHONY: all
  @@ -36,19 +36,19 @@ $(NAS2DLIB): nas2d
  nas2d:
  $(MAKE) -C nas2d-core
  -$(OBJS): $(OBJDIR)/%.o : $(SRCDIR)/%.cpp $(OBJDIR)/%.d | build-folder
  +$(OBJS): $(OBJDIR)%.o : $(SRCDIR)%.cpp $(OBJDIR)%.d | build-folder
  $(COMPILE.cpp) $(OUTPUT_OPTION) $<
  $(POSTCOMPILE)
  .PHONY: build-folder
  build-folder:
  - @mkdir -p $(patsubst $(SRCDIR)/%,$(OBJDIR)/%, $(FOLDERS))
  - @mkdir -p $(patsubst $(SRCDIR)/%,$(OBJDIR)/%, $(FOLDERS))
  + @mkdir -p $(patsubst $(SRCDIR)%,$(OBJDIR)%, $(FOLDERS))
  + @mkdir -p $(patsubst $(SRCDIR)%,$(OBJDIR)%, $(FOLDERS))
  -$(OBJDIR)/%.d: ;
  -.PRECIOUS: $(OBJDIR)/%.d
  +$(OBJDIR)%.d: ;
  +.PRECIOUS: $(OBJDIR)%.d
  -include $(wildcard $(patsubst $(SRCDIR)/%.cpp,$(OBJDIR)/%.d,$(SRCS)))
  +include $(wildcard $(patsubst $(SRCDIR)%.cpp,$(OBJDIR)%.d,$(SRCS)))
  .PHONY: clean clean-all
  clean:
  