diff --git a/src/conf.cpp b/src/conf.cpp
index bb39aa6..9a41bc1 100644
--- a/src/conf.cpp
+++ b/src/conf.cpp
@@ -101,16 +101,42 @@ const std::string& get_conf(const std::string& name)
 	return itor->second;
 }
 
+bool g_redownload = false;
+bool g_redecompress = false;
 bool g_clean = false;
+bool g_dry = false;
+bool g_verbose = false;
 
+bool conf::verbose()          { return g_verbose; }
+bool conf::dry()              { return g_dry; }
+bool conf::redownload()       { return g_redownload; }
+bool conf::redecompress()     { return g_redecompress; }
+bool conf::clean()            { return g_clean; }
 
-bool conf::verbose()          { return true; }
-bool conf::dry()              { return false; }
 std::string conf::mo_org()    { return "ModOrganizer2"; }
 std::string conf::mo_branch() { return "master"; }
-bool conf::clean()            { return  g_clean; }
 
-void conf::set_clean(bool b)  { g_clean = b; }
+void conf::set(int argc, char** argv)
+{
+	for (int i=0; i<argc; ++i)
+	{
+		const std::string a = argv[i];
+
+		if (a == "--redownload")
+			g_redownload = true;
+		else if (a == "--redecompress")
+			g_redecompress = true;
+		else if (a == "--clean")
+			g_clean = true;
+		else if (a == "--dry")
+			g_dry = true;
+		else if (a == "--verbose")
+			g_verbose = true;
+		else if (a.starts_with("--"))
+			bail_out("unknown option " + a);
+	}
+}
+
 
 fs::path third_party::sevenz()  { return "7z"; }
 fs::path third_party::jom()     { return "jom"; }
diff --git a/src/conf.h b/src/conf.h
index d14189c..abbda30 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -5,13 +5,16 @@ namespace mob
 
 struct conf
 {
+	static void set(int argc, char** argv);
+
 	static bool verbose();
 	static bool dry();
+	static bool redownload();
+	static bool redecompress();
+	static bool clean();
+
 	static std::string mo_org();
 	static std::string mo_branch();
-
-	static bool clean();
-	static void set_clean(bool b);
 };
 
 struct third_party
diff --git a/src/main.cpp b/src/main.cpp
index 0f274f3..aa9e536 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -67,13 +67,13 @@ int run(int argc, char** argv)
 		{
 			std::vector<std::string> tasks;
 
+			conf::set(argc, argv);
+
 			for (int i=1; i<argc; ++i)
 			{
 				const std::string arg = argv[i];
 
-				if (arg == "--clean")
-					conf::set_clean(true);
-				else
+				if (!arg.starts_with("--"))
 					tasks.push_back(arg);
 			}
 
diff --git a/src/op.cpp b/src/op.cpp
index bcf9c60..ffc577f 100644
--- a/src/op.cpp
+++ b/src/op.cpp
@@ -24,11 +24,22 @@ void op::create_directories(const fs::path& p)
 		do_create_directories(p);
 }
 
-void op::delete_directory(const fs::path& p)
+void op::delete_directory(const fs::path& p, flags f)
 {
 	debug("deleting directory " + p.string());
 	check(p);
 
+	if (!fs::exists(p))
+	{
+		if (f & optional)
+		{
+			debug("not deleting directory " + p.string() + ", doesn't exist");
+			return;
+		}
+
+		bail_out("can't delete directory " + p.string() + ", doesn't exist");
+	}
+
 	if (fs::exists(p) && !fs::is_directory(p))
 		bail_out(p.string() + " is not a directory");
 
@@ -36,14 +47,22 @@ void op::delete_directory(const fs::path& p)
 		do_delete_directory(p);
 }
 
-void op::delete_file(const fs::path& p)
+void op::delete_file(const fs::path& p, flags f)
 {
-	if (!fs::exists(p))
-		return;
-
 	debug("deleting file " + p.string());
 	check(p);
 
+	if (!fs::exists(p))
+	{
+		if (f & optional)
+		{
+			debug("not deleting file " + p.string() + ", doesn't exist");
+			return;
+		}
+
+		bail_out("can't delete file " + p.string() + ", doesn't exist");
+	}
+
 	if (fs::exists(p) && !fs::is_regular_file(p))
 		bail_out("can't delete " + p.string() + ", not a file");
 
@@ -166,7 +185,7 @@ void op::move_to_directory(const fs::path& src, const fs::path& dest_dir)
 }
 
 void op::copy_file_to_dir_if_better(
-	const fs::path& file, const fs::path& dir, copy_flags f)
+	const fs::path& file, const fs::path& dir, flags f)
 {
 	check(file);
 	check(dir);
@@ -236,9 +255,6 @@ void op::do_create_directories(const fs::path& p)
 
 void op::do_delete_directory(const fs::path& p)
 {
-	if (!fs::exists(p))
-		return;
-
 	std::error_code ec;
 	fs::remove_all(p, ec);
 
diff --git a/src/op.h b/src/op.h
index 541facc..4899249 100644
--- a/src/op.h
+++ b/src/op.h
@@ -8,23 +8,22 @@ namespace mob
 class op
 {
 public:
-	enum copy_flags
+	enum flags
 	{
-		no_copy_flags=0,
+		noflags = 0,
 		optional = 1
 	};
 
 	static void touch(const fs::path& p);
 	static void create_directories(const fs::path& p);
-	static void delete_directory(const fs::path& p);
-	static void delete_file(const fs::path& p);
+	static void delete_directory(const fs::path& p, flags f=noflags);
+	static void delete_file(const fs::path& p, flags f=noflags);
 	static void remove_readonly(const fs::path& first);
 	static void rename(const fs::path& src, const fs::path& dest);
 	static void move_to_directory(const fs::path& src, const fs::path& dest_dir);
 
 	static void copy_file_to_dir_if_better(
-		const fs::path& file, const fs::path& dest_dir,
-		copy_flags f=no_copy_flags);
+		const fs::path& file, const fs::path& dest_dir, flags f=noflags);
 
 private:
 	static void do_touch(const fs::path& p);
diff --git a/src/tasks/openssl.cpp b/src/tasks/openssl.cpp
index 4f17115..bfa3271 100644
--- a/src/tasks/openssl.cpp
+++ b/src/tasks/openssl.cpp
@@ -14,6 +14,11 @@ fs::path openssl::source_path()
 	return paths::build() / ("openssl-" + versions::openssl());
 }
 
+fs::path openssl::build_path()
+{
+	return source_path() / "build";
+}
+
 void openssl::do_fetch()
 {
 	const auto file = run_tool(downloader(source_url()));
@@ -104,12 +109,6 @@ fs::path openssl::include_path()
 	return openssl::source_path() / "include";
 }
 
-fs::path openssl::build_path()
-{
-	return source_path() / "build";
-}
-
-
 url openssl::source_url()
 {
 	return
diff --git a/src/tasks/pyqt.cpp b/src/tasks/pyqt.cpp
index 6a5813b..9f7705b 100644
--- a/src/tasks/pyqt.cpp
+++ b/src/tasks/pyqt.cpp
@@ -14,6 +14,11 @@ fs::path pyqt::source_path()
 	return paths::build() / ("PyQt5-" + versions::pyqt());
 }
 
+fs::path pyqt::build_path()
+{
+	return source_path() / "build";
+}
+
 void pyqt::do_fetch()
 {
 	const auto file = run_tool(downloader(source_url()));
@@ -64,8 +69,7 @@ void pyqt::do_build_and_install()
 		// sip-install.exe has trouble with deleting the build/ directory and
 		// trying to recreate it to fast, giving an access denied error; do it
 		// here instead
-		if (fs::exists(source_path() / "build"))
-			op::delete_directory(source_path() / "build");
+		op::delete_directory(source_path() / "build", op::optional);
 
 		run_tool(process_runner(process()
 			.binary(sip::sip_install_exe())
@@ -73,7 +77,7 @@ void pyqt::do_build_and_install()
 			.arg("--verbose")
 			.arg("--pep484-pyi")
 			.arg("--link-full-dll")
-			.arg("--build-dir", build_dir())
+			.arg("--build-dir", build_path())
 			.arg("--enable", "pylupdate")  // these are not in modules so they
 			.arg("--enable", "pyrcc")      // don't get copied below
 			.args(zip(repeat("--enable"), modules))
@@ -139,11 +143,6 @@ url pyqt::source_url()
 		"PyQt5-" + versions::pyqt() + ".tar.gz";
 }
 
-fs::path pyqt::build_dir()
-{
-	return source_path() / "build";
-}
-
 fs::path pyqt::sip_install_file()
 {
 	return "PyQt5_sip-" + versions::pyqt_sip() + ".tar.gz";
diff --git a/src/tasks/python.cpp b/src/tasks/python.cpp
index dd274e5..14c8069 100644
--- a/src/tasks/python.cpp
+++ b/src/tasks/python.cpp
@@ -42,6 +42,11 @@ fs::path python::source_path()
 	return paths::build() / ("python-" + s);
 }
 
+fs::path python::build_path()
+{
+	return source_path() / "PCBuild" / "amd64";
+}
+
 void python::do_fetch()
 {
 	run_tool(git_clone()
@@ -121,11 +126,6 @@ void python::install_pip()
 		.arg("-m", "ensurepip")));
 }
 
-fs::path python::build_path()
-{
-	return source_path() / "PCBuild" / "amd64";
-}
-
 fs::path python::python_exe()
 {
 	return build_path() / "python.exe";
diff --git a/src/tasks/sevenz.cpp b/src/tasks/sevenz.cpp
index 6f3f62b..d1c3ca9 100644
--- a/src/tasks/sevenz.cpp
+++ b/src/tasks/sevenz.cpp
@@ -37,6 +37,11 @@ void sevenz::do_build_and_install()
 		paths::install_dlls());
 }
 
+void sevenz::do_clean()
+{
+	op::delete_directory(module_to_build() / "x64", op::optional);
+}
+
 url sevenz::source_url()
 {
 	return "https://www.7-zip.org/a/7z" + version_for_url() + "-src.7z";
diff --git a/src/tasks/task.cpp b/src/tasks/task.cpp
index f874931..8025616 100644
--- a/src/tasks/task.cpp
+++ b/src/tasks/task.cpp
@@ -1,7 +1,8 @@
 #include "pch.h"
 #include "task.h"
+#include "../conf.h"
+#include "../op.h"
 #include "../tools.h"
-#include "../utility.h"
 
 namespace mob
 {
@@ -85,6 +86,9 @@ void task::run()
 	{
 		try
 		{
+			if (conf::clean())
+				clean();
+
 			check_interrupted();
 			fetch();
 			check_interrupted();
@@ -136,6 +140,10 @@ void task::build_and_install()
 	do_build_and_install();
 }
 
+void task::clean()
+{
+	do_clean();
+}
 
 void task::check_interrupted()
 {
diff --git a/src/tasks/task.h b/src/tasks/task.h
index 6769071..83a22a2 100644
--- a/src/tasks/task.h
+++ b/src/tasks/task.h
@@ -29,21 +29,25 @@ public:
 	static void interrupt_all();
 
 	const std::string& name() const;
+
 	virtual fs::path get_source_path() const = 0;
 
 	void run();
 	void interrupt();
 	void join();
+
 	void fetch();
 	void build_and_install();
+	void clean();
 
 protected:
 	task(std::string name);
 
 	void check_interrupted();
 
-	virtual void do_fetch() {};
-	virtual void do_build_and_install() {};
+	virtual void do_fetch() {}
+	virtual void do_build_and_install() {}
+	virtual void do_clean() {}
 
 	template <class Tool>
 	auto run_tool(Tool&& t)
diff --git a/src/tasks/tasks.h b/src/tasks/tasks.h
index 2173ab1..01db1be 100644
--- a/src/tasks/tasks.h
+++ b/src/tasks/tasks.h
@@ -181,6 +181,7 @@ class openssl : public basic_task<openssl>
 {
 public:
 	openssl();
+
 	static fs::path source_path();
 	static fs::path include_path();
 
@@ -195,8 +196,8 @@ private:
 	void copy_dlls_to(const fs::path& dir);
 	void copy_pdbs_to(const fs::path& dir);
 
-	static fs::path build_path();
 	static url source_url();
+	static fs::path build_path();
 	static std::vector<std::string> output_names();
 	static std::smatch parse_version();
 	static std::string version_no_tags();
@@ -208,7 +209,6 @@ class pyqt : public basic_task<pyqt>
 {
 public:
 	pyqt();
-
 	static fs::path source_path();
 
 protected:
@@ -216,8 +216,8 @@ protected:
 	void do_build_and_install() override;
 
 	static url source_url();
-	static fs::path build_dir();
 	static fs::path sip_install_file();
+	static fs::path build_path();
 };
 
 
@@ -278,6 +278,7 @@ public:
 protected:
 	void do_fetch() override;
 	void do_build_and_install() override;
+	void do_clean() override;
 
 private:
 	static url source_url();
diff --git a/src/tools.cpp b/src/tools.cpp
index f40e425..f7a6704 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -126,7 +126,12 @@ void downloader::do_run()
 	for (auto&& u : urls_)
 	{
 		const auto file = path_for_url(u);
-		if (fs::exists(file))
+
+		if (conf::redownload())
+		{
+			op::delete_file(file, op::optional);
+		}
+		else if (fs::exists(file))
 		{
 			file_ = file;
 			debug("download " + file_.string() + " already exists");
@@ -281,7 +286,11 @@ decompresser& decompresser::output(const fs::path& dir)
 
 void decompresser::do_run()
 {
-	if (fs::exists(interrupt_file()))
+	if (conf::redecompress())
+	{
+		op::delete_directory(where_, op::optional);
+	}
+	else if (fs::exists(interrupt_file()))
 	{
 		debug("found interrupt file " + interrupt_file().string());
 		info("previous decompression was interrupted; resuming");
@@ -559,8 +568,11 @@ void cmake::do_run()
 	{
 		for (auto&& [k, g] : all_generators())
 		{
-			op::delete_directory(root_ / g.output_dir(arch::x86));
-			op::delete_directory(root_ / g.output_dir(arch::x64));
+			op::delete_directory(
+				root_ / g.output_dir(arch::x86), op::optional);
+
+			op::delete_directory(
+				root_ / g.output_dir(arch::x64), op::optional);
 		}
 	}
 
diff --git a/src/utility.cpp b/src/utility.cpp
index b16fed3..b84dc76 100644
--- a/src/utility.cpp
+++ b/src/utility.cpp
@@ -170,8 +170,7 @@ file_deleter::~file_deleter()
 
 void file_deleter::delete_now()
 {
-	if (fs::exists(p_))
-		op::delete_file(p_);
+	op::delete_file(p_, op::optional);
 }
 
 void file_deleter::cancel()
@@ -193,8 +192,7 @@ directory_deleter::~directory_deleter()
 
 void directory_deleter::delete_now()
 {
-	if (fs::exists(p_))
-		op::delete_directory(p_);
+	op::delete_directory(p_, op::optional);
 }
 
 void directory_deleter::cancel()