diff --git a/.luaurc b/.luaurc
index d1ae244..5518c4c 100644
--- a/.luaurc
+++ b/.luaurc
@@ -4,6 +4,7 @@
         "testkit": "tools/testkit",
         "mirror": "mirror",
         "tools": "tools",
+        "addons": "addons",
     },
     "languageMode": "strict"
 }
diff --git a/tools/entity_visualiser.luau b/addons/entity_visualiser.luau
similarity index 66%
rename from tools/entity_visualiser.luau
rename to addons/entity_visualiser.luau
index 69dc910..f3c3c7e 100644
--- a/tools/entity_visualiser.luau
+++ b/addons/entity_visualiser.luau
@@ -1,7 +1,40 @@
 local jecs = require("@jecs")
 local ECS_GENERATION = jecs.ECS_GENERATION
 local ECS_ID = jecs.ECS_ID
-local ansi = require("@tools/ansi")
+
+local ansi = {
+	white_underline = function(s: any)
+		return `\27[1;4m{s}\27[0m`
+	end,
+
+	white = function(s: any)
+		return `\27[37;1m{s}\27[0m`
+	end,
+
+	green = function(s: any)
+		return `\27[32;1m{s}\27[0m`
+	end,
+
+	red = function(s: any)
+		return `\27[31;1m{s}\27[0m`
+	end,
+
+	yellow = function(s: any)
+		return `\27[33;1m{s}\27[0m`
+	end,
+
+	red_highlight = function(s: any)
+		return `\27[41;1;30m{s}\27[0m`
+	end,
+
+	green_highlight = function(s: any)
+		return `\27[42;1;30m{s}\27[0m`
+	end,
+
+	gray = function(s: any)
+		return `\27[30;1m{s}\27[0m`
+	end,
+}
 
 local function pe(e: any)
 	local gen = ECS_GENERATION(e)
diff --git a/tools/lifetime_tracker.luau b/addons/lifetime_tracker.luau
similarity index 93%
rename from tools/lifetime_tracker.luau
rename to addons/lifetime_tracker.luau
index c9abbbf..54d9ee9 100644
--- a/tools/lifetime_tracker.luau
+++ b/addons/lifetime_tracker.luau
@@ -4,10 +4,9 @@ local ECS_ID = jecs.ECS_ID
 local __ = jecs.Wildcard
 local pair = jecs.pair
 
-local prettify = require("@tools/entity_visualiser").prettify
+local prettify = require("@addons/entity_visualiser").prettify
 
 local pe = prettify
-local ansi = require("@tools/ansi")
 
 function print_centered_entity(entity, width: number)
 	local entity_str = tostring(entity)
@@ -40,12 +39,10 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 
 	local ENTITY_RANGE = (jecs.Rest :: any) + 1
 
-	local w = setmetatable({}, { __index = world })
-
 	padding_enabled = opt.padding_enabled
 
 	local world_entity = world.entity
-	w.entity = function(self, entity)
+	world.entity = function(_, entity)
 		if entity then
 			return world_entity(world, entity)
 		end
@@ -59,7 +56,7 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 		pad()
 		return e
 	end
-	w.print_entity_index = function(self)
+	world.print_entity_index = function()
 		local max_id = entity_index.max_id
 		local alive_count = entity_index.alive_count
 		local alive = table.move(dense_array, 1 + jecs.Rest :: any, alive_count, 1, {})
@@ -86,7 +83,7 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 		pad()
 	end
 	local timelines = {}
-	w.print_snapshot = function(self)
+	world.print_snapshot = function(_)
 		local timeline = #timelines + 1
 		local entity_column_width = 10
 		local status_column_width = 8
@@ -161,7 +158,7 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 	end
 	local world_add = world.add
 	local relations = {}
-	w.add = function(self, entity: any, component: any)
+	world.add = function(_, entity: any, component: any)
 		world_add(world, entity, component)
 		if jecs.IS_PAIR(component) then
 			local relation = jecs.pair_first(world, component)
@@ -172,7 +169,7 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 	end
 
 	local world_delete = world.delete
-	w.delete = function(self, e)
+	world.delete = function(world, e)
 		world_delete(world, e)
 
 		local idr_t = component_index[pair(__, e)]
@@ -210,7 +207,7 @@ local function lifetime_tracker_add(world: jecs.World, opt)
 		print(`*deleted {pe(e)}`)
 		pad()
 	end
-	return w
+	return world
 end
 
 return lifetime_tracker_add
diff --git a/tools/observers.luau b/addons/observers.luau
similarity index 72%
rename from tools/observers.luau
rename to addons/observers.luau
index 6090adf..9afad4e 100644
--- a/tools/observers.luau
+++ b/addons/observers.luau
@@ -1,11 +1,9 @@
 local jecs = require("@jecs")
 local testkit = require("@testkit")
 
-local function observers_new(description)
-	local event = description.event
+local function observers_new(world, description)
 	local query = description.query
 	local callback = description.callback
-	local world = query.world
 	local terms = query.filter_with
 	if not terms then
 		local ids = query.ids
@@ -26,11 +24,8 @@ local function observers_new(description)
 	end
 
 	for _, term in terms do
-		if event == jecs.OnAdd then
-			world:added(term, emplaced)
-		elseif event == jecs.OnSet then
-			world:emplaced(term, emplaced)
-		end
+		world:added(term, emplaced)
+		world:changed(term, emplaced)
  	end
 end
 
@@ -67,12 +62,11 @@ local function world_track(world, ...)
 
 	for _, term in terms do
 		world:added(term, emplaced)
-		world:emplaced(term, emplaced)
+		world:changed(term, emplaced)
  	end
 
 	local function iter()
 		local i = n
-		print(i, "i")
 		return function()
 			local row = i
 			if row == 0 then
@@ -84,12 +78,16 @@ local function world_track(world, ...)
 	end
 
 	local it = {
-		__iter = iter
+		__iter = iter,
+		without = function(self, ...)
+			q_shim.filter_without = { ... }
+			return self
+		end
 	}
 	return setmetatable(it, it)
 end
 
-local function observers_init(world)
+local function observers_add(world)
 	local signals = {
 		added = {},
 		emplaced = {},
@@ -110,13 +108,13 @@ local function observers_init(world)
 		table.insert(listeners, fn)
 	end
 
-	world.emplaced = function(_, component, fn)
+	world.changed = function(_, component, fn)
 		local listeners = signals.emplaced[component]
 		if not listeners then
 			listeners = {}
 			signals.emplaced[component] = listeners
 			local idr = jecs.id_record_ensure(world, component)
-			idr.hooks.on_set = function(entity, value)
+			idr.hooks.on_change = function(entity, value)
 				for _, listener in listeners do
 					listener(entity, value)
 				end
@@ -143,46 +141,9 @@ local function observers_init(world)
 	world.signals = signals
 
 	world.track = world_track
-	return
+
+	world.observer = observers_new
+	return world
 end
 
-local world = jecs.world()
-observers_init(world)
-
-local A = world:component()
-local B = world:component()
-
-world:added(A, print)
-world:added(A, function(entity)
-	print(entity, 2)
-end)
-
-local observer = observers_new({
-	event = jecs.OnAdd,
-	query = world:query(A, B),
-	callback = function(entity)
-		print(entity, 3)
-	end
-})
-
-local e = world:entity()
-local Test = world:track(A, B)
-for a in Test do
-	print(a)
-	assert(false)
-end
-world:add(e, A)
-
--- Output:
---  271
---  271, 2
-for _ in Test do
-	assert(false)
-end
-world:add(e, B)
-for a in Test do
-	print("lol")
-	assert(true)
-end
--- Output:
---  271, 3
+return observers_add
diff --git a/test/devtools_test.luau b/test/addons/entity_visualiser.luau
similarity index 83%
rename from test/devtools_test.luau
rename to test/addons/entity_visualiser.luau
index 31ed1df..e011041 100644
--- a/test/devtools_test.luau
+++ b/test/addons/entity_visualiser.luau
@@ -1,8 +1,7 @@
 local jecs = require("@jecs")
 local pair = jecs.pair
 local ChildOf = jecs.ChildOf
-local lifetime_tracker_add = require("@tools/lifetime_tracker")
-local pe = require("@tools/entity_visualiser").prettify
+local lifetime_tracker_add = require("@addons/lifetime_tracker")
 local world = lifetime_tracker_add(jecs.world(), {padding_enabled=false})
 local FriendsWith = world:component()
 world:print_snapshot()
diff --git a/test/addons/observers.luau b/test/addons/observers.luau
new file mode 100644
index 0000000..616f5e9
--- /dev/null
+++ b/test/addons/observers.luau
@@ -0,0 +1,46 @@
+local jecs = require("@jecs")
+local observers_add = require("@addons/observers")
+
+local world = jecs.world()
+observers_add(world)
+
+local A = world:component()
+local B = world:component()
+local C = world:component()
+
+world:observer({
+	query = world:query(),
+	callback = function(entity)
+		buf ..= debug.info(2, "sl")
+	end
+})
+
+local i = 0
+world:added(A, function(entity)
+	assert(i == 0)
+	i += 1
+end)
+world:added(A, function(entity)
+	assert(i == 1)
+	i += 1
+end)
+
+world:removed(A, function(entity)
+	assert(false)
+end)
+
+local observer = world:observer({
+	query = world:query(A, B),
+	callback = function(entity)
+		assert(i == 2)
+		i += 1
+	end
+})
+
+
+local e = world:entity()
+world:add(e, A)
+assert(i == 2)
+
+world:add(e, B)
+assert(i == 3)
diff --git a/test/tests.luau b/test/tests.luau
index 002b4af..ce0f9fd 100644
--- a/test/tests.luau
+++ b/test/tests.luau
@@ -133,6 +133,8 @@ TEST("#adding a recycled target", function()
 
 end)
 
+local entity_visualizer = require("@addons/entity_visualiser")
+
 TEST("#repro2", function()
 	local world = world_new()
 	local Lifetime = world:component() :: jecs.Id<number>
@@ -144,7 +146,6 @@ TEST("#repro2", function()
 	world:set(entity, pair(Lifetime, Beam), 2)
 	world:set(entity, pair(4, 5), 6) -- noise
 
-	local entity_visualizer = require("@tools/entity_visualiser")
 	-- entity_visualizer.components(world, entity)
 
 	for e in world:each(pair(Lifetime, __)) do
@@ -169,7 +170,7 @@ TEST("#repro2", function()
 	CHECK(world:get(entity, pair(Lifetime, Beam)) == 1)
 end)
 
-local lifetime_tracker_add = require("@tools/lifetime_tracker")
+local lifetime_tracker_add = require("@addons/lifetime_tracker")
 
 TEST("another", function()
 	local world = world_new()
@@ -306,8 +307,8 @@ TEST("world:cleanup()", function()
 	CHECK(#archetype_index["1_2_3"].entities == 1)
 end)
 
-local pe = require("@tools/entity_visualiser").prettify
-local lifetime_tracker_add = require("@tools/lifetime_tracker")
+local pe = require("@addons/entity_visualiser").prettify
+local lifetime_tracker_add = require("@addons/lifetime_tracker")
 
 TEST("world:entity()", function()
 	do
diff --git a/tools/ansi.luau b/tools/ansi.luau
deleted file mode 100644
index a391f8e..0000000
--- a/tools/ansi.luau
+++ /dev/null
@@ -1,33 +0,0 @@
-return {
-	white_underline = function(s: any)
-		return `\27[1;4m{s}\27[0m`
-	end,
-
-	white = function(s: any)
-		return `\27[37;1m{s}\27[0m`
-	end,
-
-	green = function(s: any)
-		return `\27[32;1m{s}\27[0m`
-	end,
-
-	red = function(s: any)
-		return `\27[31;1m{s}\27[0m`
-	end,
-
-	yellow = function(s: any)
-		return `\27[33;1m{s}\27[0m`
-	end,
-
-	red_highlight = function(s: any)
-		return `\27[41;1;30m{s}\27[0m`
-	end,
-
-	green_highlight = function(s: any)
-		return `\27[42;1;30m{s}\27[0m`
-	end,
-
-	gray = function(s: any)
-		return `\27[30;1m{s}\27[0m`
-	end,
-}