diff --git a/tools/build b/tools/build
index 0ba47ef..9bd86b1 100755
--- a/tools/build
+++ b/tools/build
@@ -1,14 +1,40 @@
-#!/usr/bin/env bash
+#!/usr/bin/env python3
 
-## args
-
-if [ $# -ge 1 ] ; then arg1=$1 && shift ; else arg1="" ; fi
+import os as _os
+import argparse as _argparse
 
 
-## exec
+def main():
+	## args
+	argument_parser = _argparse.ArgumentParser()
+	argument_parser.add_argument(
+		"--output-directory",
+		"-o",
+		type = str,
+		default = "build",
+		help = "output directory",
+	)
+	argument_parser.add_argument(
+		"--tests",
+		"-t",
+		action = "store_true",
+		default = False,
+		help = "whether to also build the test routines",
+	)
+	args = argument_parser.parse_args()
+	
+	## exec
+	targets = []
+	targets.append("main")
+	if args.tests:
+		targets.append("test")
+	_os.system(
+		"make dir_build=%s --file=tools/makefile %s"
+		% (
+			args.output_directory,
+			" ".join(targets),
+		)
+	)
+	
 
-targets=""
-targets="${targets} build/espe"
-if [ ${arg1} == "-t" ] ; then targets="${targets} test" ; fi
-
-make --file=tools/makefile ${targets}
+main()
diff --git a/tools/makefile b/tools/makefile
index 8c1033a..afd39f6 100644
--- a/tools/makefile
+++ b/tools/makefile
@@ -17,11 +17,8 @@ cmd_cp := cp
 .PHONY: default
 default: main
 
-.PHONY: main
-main: node_modules ${dir_build}/espe
-
-.PHONY: test
-test: ${dir_build}/espe-test.mocha.js
+.PHONY: core
+core: node_modules ${dir_temp}/espe-core.js ${dir_temp}/espe-core.d.ts
 
 .PHONY: node_modules
 node_modules:
@@ -55,6 +52,9 @@ ${dir_temp}/espe-core.js ${dir_temp}/espe-core.d.ts: \
 	@ ${cmd_mkdir} $(dir $@)
 	@ tsc --lib es2020 $^ --outFile ${dir_temp}/espe-core.js --declaration
 
+.PHONY: main
+main: core ${dir_build}/espe
+
 ${dir_temp}/espe-main-raw.js: \
 		${dir_lib}/plankton/plankton.d.ts \
 		${dir_temp}/espe-core.d.ts \
@@ -63,15 +63,6 @@ ${dir_temp}/espe-main-raw.js: \
 	@ ${cmd_mkdir} $(dir $@)
 	@ tsc --lib es2020 $^ --outFile $@
 
-${dir_temp}/espe-test-raw.js: \
-		${dir_lib}/plankton/plankton.d.ts \
-		${dir_temp}/espe-core.d.ts \
-		${dir_lib}/node/node_modules/@types/mocha/index.d.ts \
-		${dir_source}/tests.mocha.ts
-	@ ${cmd_log} "compile | test …"
-	@ ${cmd_mkdir} $(dir $@)
-	@ tsc --lib es2020 $^ --outFile $@
-
 ${dir_build}/espe: \
 		${dir_source}/head.js \
 		${dir_lib}/plankton/plankton.js \
@@ -82,6 +73,18 @@ ${dir_build}/espe: \
 	@ ${cmd_cat} $^ > $@
 	@ ${cmd_chmod} +x $@
 
+.PHONY: test
+test: core ${dir_build}/espe-test.mocha.js
+
+${dir_temp}/espe-test-raw.js: \
+		${dir_lib}/plankton/plankton.d.ts \
+		${dir_temp}/espe-core.d.ts \
+		${dir_lib}/node/node_modules/@types/mocha/index.d.ts \
+		${dir_source}/tests.mocha.ts
+	@ ${cmd_log} "compile | test …"
+	@ ${cmd_mkdir} $(dir $@)
+	@ tsc --lib es2020 $^ --outFile $@
+
 ${dir_build}/espe-test.mocha.js: \
 		${dir_source}/head.js \
 		${dir_lib}/plankton/plankton.js \