I question some people (#28208)

code/__DEFINES/_math.dm

@@ -63,9 +63,9 @@
 
 #define ISABOUTEQUAL(a, b, deviation) (deviation ? abs((a) - (b)) <= deviation : abs((a) - (b)) <= 0.1)
 
-#define ISEVEN(x) (x % 2 == 0)
+#define ISEVEN(x) (!((x) & 1))
 
-#define ISODD(x) (x % 2 != 0)
+#define ISODD(x) ((x) & 1)
 
 // Returns true if val is from min to max, inclusive.
 #define ISINRANGE(val, min, max) (min <= val && val <= max)

code/__DEFINES/hud.dm

@@ -77,7 +77,7 @@
 
 /proc/ui_hand_position(i)
 	// values based on old hand ui positions (CENTER:-/+16,SOUTH:5)
-	var/x_off = i % 2 ? 0 : -1
+	var/x_off = ISODD(i) ? 0 : -1
 	var/y_off = round((i-1) / 2)
 	return"CENTER+[x_off]:16,SOUTH+[y_off]:5"