diff --git a/Makefile b/Makefile
index 986928e..fdca348 100644
--- a/Makefile
+++ b/Makefile
@@ -1,33 +1,33 @@
-# Universal makefile for single C++ program
-#
-# Use gcc flag -MMD (user) or -MD (user/system) to generate dependencies among source files.
-# Use make default rules for commonly used file-name suffixes and make variables names.
-#
-# % make [ a.out ]
-
-########## Variables ##########
-
-CXX = g++					# compiler
-CXXFLAGS = -std=c++20 -g -Wall -MMD -O0			# compiler flags
-MAKEFILE_NAME = ${firstword ${MAKEFILE_LIST}}	# makefile name
-
-SOURCES = $(wildcard src/*.cc)			# source files (*.cc)
-OBJECTS = ${SOURCES:.cc=.o}			# object files forming executable
-DEPENDS = ${OBJECTS:.o=.d}			# substitute ".o" with ".d"
-EXEC	= bin/cc3k					# executable name
-
-########## Targets ##########
-
-.PHONY : clean					# not file names
-
-${EXEC} : ${OBJECTS}				# link step
-	${CXX} ${CXXFLAGS} $^ -o $@ -lncurses		# additional object files before $^
-
-${OBJECTS} : ${MAKEFILE_NAME}			# OPTIONAL : changes to this file => recompile
-
-# make implicitly generates rules to compile C++ files that generate .o files
-
--include ${DEPENDS}				# include *.d files containing program dependences
-
-clean :						# remove files that can be regenerated
-	rm -f ${DEPENDS} ${OBJECTS} ${EXEC}
+# Universal makefile for single C++ program
+#
+# Use gcc flag -MMD (user) or -MD (user/system) to generate dependencies among source files.
+# Use make default rules for commonly used file-name suffixes and make variables names.
+#
+# % make [ a.out ]
+
+########## Variables ##########
+
+CXX = g++						# compiler
+CXXFLAGS = -std=c++20 -g -Wall -MMD -O0			# compiler flags
+MAKEFILE_NAME = ${firstword ${MAKEFILE_LIST}}		# makefile name
+
+SOURCES = $(wildcard src/*.cc)				# source files (*.cc)
+OBJECTS = ${SOURCES:.cc=.o}				# object files forming executable
+DEPENDS = ${OBJECTS:.o=.d}				# substitute ".o" with ".d"
+EXEC	= bin/cc3k					# executable name
+
+########## Targets ##########
+
+.PHONY : clean						# not file names
+
+${EXEC} : ${OBJECTS}					# link step
+	${CXX} ${CXXFLAGS} -O0 $^ -o $@ -lncurses	# additional object files before $^
+
+${OBJECTS} : ${MAKEFILE_NAME}				# OPTIONAL : changes to this file => recompile
+
+# make implicitly generates rules to compile C++ files that generate .o files
+
+-include ${DEPENDS}					# include *.d files containing program dependences
+
+clean :							# remove files that can be regenerated
+	rm -f ${DEPENDS} ${OBJECTS} ${EXEC}
diff --git a/bin/.keep_dir b/bin/.keep_dir
new file mode 100644
index 0000000..e69de29