diff --git a/all.h b/all.h
index 59718c1..2a9199a 100644
--- a/all.h
+++ b/all.h
@@ -185,6 +185,13 @@
 
 #define stmnt(S) do{ S }while(0)
 
+#ifndef STATIC_ASSERT
+	#define STATIC_ASSERT3(cond, msg) typedef char static_assertion_##msg[(!!(cond))*2-1]
+	#define STATIC_ASSERT2(cond, line) STATIC_ASSERT3(cond, static_assertion_at_line_##line)
+	#define STATIC_ASSERT1(cond, line) STATIC_ASSERT2(cond, line)
+	#define STATIC_ASSERT(cond)        STATIC_ASSERT1(cond, __LINE__)
+#endif
+
 #if !defined(assertBreak)
 # define assertBreak() (*(volatile int*)0 = 0)
 #endif
@@ -260,6 +267,17 @@ typedef const char*           str;
 typedef float                 f32;
 typedef double                f64;
 
+STATIC_ASSERT(sizeof(u8) == 1);
+STATIC_ASSERT(sizeof(i8) == 1);
+STATIC_ASSERT(sizeof(u16) == 2);
+STATIC_ASSERT(sizeof(i16) == 2);
+STATIC_ASSERT(sizeof(u32) == 4);
+STATIC_ASSERT(sizeof(i32) == 4);
+STATIC_ASSERT(sizeof(u64) == 8);
+STATIC_ASSERT(sizeof(i64) == 8);
+STATIC_ASSERT(sizeof(f32) == 4);
+STATIC_ASSERT(sizeof(f64) == 8);
+
 //typedef long double f80; only returning 8 bytes on my mac for some reason
 /*
   printf("u8 %d\n", (int)sizeof(u8) * 8);
@@ -625,6 +643,9 @@ fn void u32ReverseArray(u32 arr[], u32 size);
 fn Vec2f32 vec2Add(Vec2 a, Vec2 b);
 fn Vec2f32 vec2Subtract(Vec2 a, Vec2 b);
 fn Vec2f32 vec2FromHexCube(Vec2 map_center, XYZ cube, f32 size, f32 border_thickness);
+fn i32 i32Middle(i32 x, i32 y);
+fn u32 u32Middle(u32 x, u32 y);
+fn u64 u64SafeMul(u64 x, u64 y);
 
 ///// MEMORY (Arenas)
 #define ARENA_MAX GB(1)
diff --git a/math.c b/math.c
index 0aeceea..b889e2f 100644
--- a/math.c
+++ b/math.c
@@ -99,3 +99,40 @@ fn Vec2f32 vec2FromHexCube(Vec2 map_center, XYZ cube, f32 size, f32 border_thick
   };
 }
 
+/* from https://graphitemaster.github.io/aau/
+T midpoint(T x, T y) {
+    // U is the unsigned version of your type T, or same as T if T already unsigned
+    // digits is the number of numeric digits (not including sign) in your type T.
+    // std::numeric_limits<T>::digits in C++ is helpful here.
+    U shift = digits - 1;
+    U difference = (U)x - (U)y;
+    U sign = y < x;
+    U half = (difference / 2) + (sign << shift) + (sign & difference);
+    T mid = (T)(x + half);
+    return mid;
+}
+ */
+
+fn i32 i32Middle(i32 x, i32 y) {
+  u32 shift = 31 - 1;
+  u32 difference = (u32)x - (u32)y;
+  u32 sign = y < x;
+  u32 half = (difference / 2) + (sign << shift) + (sign & difference);
+  i32 mid = (i32)(x + half);
+  return mid;
+}
+
+fn u32 u32Middle(u32 x, u32 y) {
+  u32 shift = 32 - 1;
+  u32 difference = (u32)x - (u32)y;
+  u32 sign = y < x;
+  u32 half = (difference / 2) + (sign << shift) + (sign & difference);
+  u32 mid = (u32)(x + half);
+  return mid;
+}
+
+fn u64 u64SafeMul(u64 x, u64 y) {
+  assert(!(y && x > MAX_u64/y));
+  return x * y;
+}
+
diff --git a/memory.c b/memory.c
index b0655ac..92f0536 100644
--- a/memory.c
+++ b/memory.c
@@ -47,7 +47,7 @@ fn void* arenaAllocZero(Arena* a, u64 size) {
 }
 
 fn void* arenaAllocArraySized(Arena* arena, u64 elem_size, u64 count) {
-    return arenaAlloc(arena, elem_size * count);
+    return arenaAlloc(arena, u64SafeMul(elem_size, count));
 }
 
 fn void arenaDealloc(Arena* arena, u64 size) {