Move more contiguous related code blocks from main.asm to engine/ and events/

engine/square_root.asm

@@ -0,0 +1,30 @@
+GetSquareRoot: ; 13b87
+; Return the square root of de in b.
+
+; Rather than calculating the result, we take the index of the
+; first value in a table of squares that isn't lower than de.
+
+	ld hl, Squares
+	ld b, 0
+.loop
+; Make sure we don't go past the end of the table.
+	inc b
+	ld a, b
+	cp $ff
+	ret z
+
+; Iterate over the table until b**2 >= de.
+	ld a, [hli]
+	sub e
+	ld a, [hli]
+	sbc d
+
+	jr c, .loop
+	ret
+
+Squares: ; 13b98
+root	set 1
+	rept $ff
+	dw root*root
+root	set root+1
+	endr