add a very basic vector2 implementation.

src/util/vec2.h

@@ -0,0 +1,34 @@
+#ifndef VEC2_H
+#define VEC2_H
+#define VEC2_COMB2(a, b) a##b
+#define VEC2_COMB1(a, b) VEC2_COMB2(a, b)
+#endif
+
+#define VEC2_TYPE int
+
+#ifdef VEC2_TYPE
+
+// customising the linkage
+#ifndef VEC2_LINKAGE
+#define VEC2_LINKAGE static inline
+#endif
+
+// customising the name
+#ifndef VEC2_NAME
+#define VEC2_NAME VEC2_COMB1(vec2_, VEC2_TYPE)
+#endif // VEC2_NAME
+
+// defines a two-dimensional vector of a specific type
+typedef struct {
+    VEC2_TYPE x;
+    VEC2_TYPE y;
+} VEC2_NAME;
+
+// TODO: implement vector-based logic
+
+#undef VEC2_NAME
+#undef VEC2_LINKAGE
+#undef VEC2_TYPE
+#elif __INCLUDE_LEVEL__ != 0
+#error define VEC2_TYPE before including
+#endif // VEC2_TYPE