diff --git a/init.lua b/init.lua
index 2acf119..08d3a1e 100644
--- a/init.lua
+++ b/init.lua
@@ -78,6 +78,9 @@ function _batteries:export()
 	--overwrite assert wholesale (it's compatible)
 	assert = self.assert
 
+	--like ipairs, but in reverse
+	ripairs = self.tablex.ripairs
+
 	--export the whole library to global `batteries`
 	batteries = self
 
diff --git a/intersect.lua b/intersect.lua
index 18b3a3c..f77d7b5 100644
--- a/intersect.lua
+++ b/intersect.lua
@@ -17,6 +17,7 @@
 
 local path = (...):gsub("intersect", "")
 local vec2 = require(path .. "vec2")
+local mathx = require(path .. "mathx")
 
 --module storage
 local intersect = {}
@@ -337,10 +338,10 @@ function intersect.aabb_aabb_collide(a_pos, a_hs, b_pos, b_hs, into)
 		--actually collided
 		if abs_amount.x <= abs_amount.y then
 			--x min
-			res = into:scalar_set(abs_amount.x * math.sign(delta.x), 0)
+			res = into:scalar_set(abs_amount.x * mathx.sign(delta.x), 0)
 		else
 			--y min
-			res = into:scalar_set(0, abs_amount.y * math.sign(delta.y))
+			res = into:scalar_set(0, abs_amount.y * mathx.sign(delta.y))
 		end
 	end
 	return res
diff --git a/tablex.lua b/tablex.lua
index 3719d88..effab38 100644
--- a/tablex.lua
+++ b/tablex.lua
@@ -417,4 +417,19 @@ function tablex.unpack8(t)
 	return t[1], t[2], t[3], t[4], t[5], t[6], t[7], t[8]
 end
 
+--internal: reverse iterator function
+local function _ripairs_iter(t, i)
+	i = i - 1
+	local v = t[i]
+	if v then
+		return i, v
+	end
+end
+
+--iterator that works like ipairs, but in reverse order, with indices from #t to 1
+--similar to ipairs, it will only consider sequential until the first nil value in the table.
+function tablex.ripairs(t)
+	return _ripairs_iter, t, #t + 1
+end
+
 return tablex