diff --git a/src/ruc/meta/core.h b/src/ruc/meta/core.h
new file mode 100644
index 0000000..03920cc
--- /dev/null
+++ b/src/ruc/meta/core.h
@@ -0,0 +1,9 @@
+/*
+ * Copyright (C) 2022 Riyyi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#define BIT(x) (1 << x)