--- Makefile.orig	2025-01-23 15:20:57.000000000 +0800
+++ Makefile	2026-04-30 18:50:12.000000000 +0800
@@ -28,12 +28,20 @@
 # - CXX: The C++ compiler, such as g++ or clang++.
 # - CXXFLAGS: Any extra user-specified compiler flags (can be blank).
 
+CXX ?= g++
+AR ?= ar
 # Recommended compiler flags:
 CXXFLAGS += -std=c++11 -O
 
 # Extra flags for diagnostics:
 # CXXFLAGS += -g -Wall -Wextra -Wpedantic -Wconversion -Wsign-conversion -fsanitize=undefined,address
 
+INSTALL ?= install
+PREFIX ?= /opt/local
+DESTDIR ?=
+BINDIR ?= $(PREFIX)/bin
+LIBDIR ?= $(PREFIX)/lib
+INCDIR ?= $(PREFIX)/include
 
 # ---- Controlling make ----
 
@@ -45,7 +53,7 @@
 
 # Stuff concerning goals
 .DEFAULT_GOAL = all
-.PHONY: all clean
+.PHONY: all install clean
 
 
 # ---- Targets to build ----
@@ -60,16 +68,22 @@
 
 # Delete build output
 clean:
-	rm -f -- $(LIBOBJ) $(LIBFILE) $(MAINS:=.o) $(MAINS)
+	rm -f $(LIBOBJ) $(LIBFILE) $(MAINS:=.o) $(MAINS)
 	rm -rf .deps
 
+install: $(LIBFILE) $(MAINS)
+	$(INSTALL) -d "$(DESTDIR)$(BINDIR)" "$(DESTDIR)$(LIBDIR)" "$(DESTDIR)$(INCDIR)"
+	$(INSTALL) -m 755 $(MAINS) "$(DESTDIR)$(BINDIR)/$(MAINS)"
+	$(INSTALL) -m 644 $(LIBFILE) "$(DESTDIR)$(LIBDIR)/$(LIBFILE)"
+	$(INSTALL) -m 644 qrcodegen.hpp "$(DESTDIR)$(INCDIR)/qrcodegen.hpp"
+
 # Executable files
 %: %.o $(LIBFILE)
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $@ $< -L . -l $(LIB)
 
 # The library
 $(LIBFILE): $(LIBOBJ)
-	$(AR) -crs $@ -- $^
+	$(AR) -crs $@ $^
 
 # Object files
 %.o: %.cpp .deps/timestamp