diff --git a/lean/include/shuffle3.h b/lean/include/shuffle3.h
new file mode 100644
index 0000000..085719a
--- /dev/null
+++ b/lean/include/shuffle3.h
@@ -0,0 +1,30 @@
+#ifndef _SHUFFLE3_H
+#define _SHUFFLE3_H
+
+#ifdef __cplusplus
+#define _UNIQUE __restrict
+extern "C" {
+#else
+#define _UNIQUE restrict
+#endif
+
+#ifdef DEBUG
+#define _FORCE_INLINE __attribute__((gnu_inline)) static inline
+#else
+#define _FORCE_INLINE __attribute__((gnu_inline)) extern inline
+#endif
+
+struct panicinfo {
+	const char* file;
+	const char* function;
+	int line;
+};
+
+void _do_panic(struct panicinfo pi, const char* fmt, ...) __attribute__((noreturn, cold));
+#define panic(fmt, ...) _do_panic( (struct panicinfo){.file = __FILE__, .function = __func__, .line = __LINE__}, fmt __VA_OPT__(,) __VA_ARGS__)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SHUFFLE3_H */
diff --git a/lean/src/main.c b/lean/src/main.c
new file mode 100644
index 0000000..0372a6d
--- /dev/null
+++ b/lean/src/main.c
@@ -0,0 +1,17 @@
+
+#include <shuffle3.h>
+
+static void shuffle_file(const char* filename)
+{
+	panic("unimplemented");
+}
+
+static void unshuffle_file(const char* filename)
+{
+	panic("unimplemented");
+}
+
+int main(int argc, char** argv)
+{
+	return 0;
+}
diff --git a/lean/src/panic.c b/lean/src/panic.c
new file mode 100644
index 0000000..b6f4b0d
--- /dev/null
+++ b/lean/src/panic.c
@@ -0,0 +1,16 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+#include <shuffle3.h>
+
+__attribute__((noreturn, cold)) void _do_panic(struct panicinfo info, const char* fmt, ...)
+{
+	va_list li;
+	va_start(li, fmt);
+	 fprintf(stderr, "[!] (%s->%s:%d) fatal error: ", info.file, info.function, info.line);
+	vfprintf(stderr, fmt, li);
+	 fprintf(stderr, "\n");
+	va_end(li);
+	abort();
+}