diff --git a/init.lua b/init.lua
index 8b5c178..9852991 100644
--- a/init.lua
+++ b/init.lua
@@ -1,6 +1,11 @@
 local Tactree = {}
 local Nodes = {}
 
+local function NodeReset(node)
+	node:_finish()
+	node._started = false
+end
+
 local function NodeStart(node, args)
 	-- don't start again if started
 	if node._started then return end
@@ -14,14 +19,27 @@ end
 
 local function NodeUpdate(node, ...)
 	-- automatically start if not started
-	if not node._started then NodeStart(node) end
+	if not node._started then
+		NodeStart(node)
+	end
+
+	-- mark node as run and unmark children
+	node._ran = true
+	for _, child in ipairs(node.children) do
+		child._ran = false
+	end
 
 	local result = node:_tick(...)
 
-	if type(result) == 'boolean' then
-		node:_finish()
+	if result ~= nil then
+		NodeReset(node)
+	end
 
-		node._started = false
+	-- reset unrun children
+	for _, child in ipairs(node.children) do
+		if not child._ran and child._started then
+			NodeReset(child)
+		end
 	end
 
 	return result
@@ -85,8 +103,8 @@ local function tree_by_name(name, depth)
 	node.update = NodeUpdate
 	node.private = NodePrivateData
 
-	-- this will crash if there is a recursive structure
-	-- find a way to prevent this?
+	-- this will crash if there is a recursive structure; find a way to prevent this?
+	-- does my API even allow declaring recursive structures?
 	if Nodes[name].children then
 		for _, child in ipairs(Nodes[name].children) do
 			local cn = tree_by_name(child, depth + 1)
@@ -137,6 +155,20 @@ function Tactree.Tree(name)
 end
 
 Tactree.Leaf 'Sequence'
+{
+	function(node, ...)
+		local child = 1
+		local result
+		repeat
+			result = node.children[child]:update(...)
+			child = child + 1
+		until (not result) or (child > #node.children)
+
+		return result
+	end
+}
+
+Tactree.Leaf 'StepSequence'
 {
 	start = function(node)
 		node:private().current_child = 1
@@ -145,9 +177,7 @@ Tactree.Leaf 'Sequence'
 		local result
 		repeat
 			result = node.children[node:private().current_child]:update(...)
-			if result then
-				node:private().current_child = node:private().current_child + 1
-			end
+			if result ~= nil then node:private().current_child = node:private().current_child + 1 end
 		until (not result) or (node:private().current_child > #node.children)
 
 		return result
@@ -155,6 +185,20 @@ Tactree.Leaf 'Sequence'
 }
 
 Tactree.Leaf 'Selector'
+{
+	function(node, ...)
+		local child = 1
+		local result
+		repeat
+			result = node.children[child]:update(...)
+			child = child + 1
+		until (result ~= false) or (child > #node.children)
+
+		return result
+	end
+}
+
+Tactree.Leaf 'StepSelector'
 {
 	start = function(node)
 		node:private().current_child = 1
@@ -163,9 +207,7 @@ Tactree.Leaf 'Selector'
 		local result
 		repeat
 			result = node.children[node:private().current_child]:update(...)
-			if result == false then
-				node:private().current_child = node:private().current_child + 1
-			end
+			if result ~= nil then node:private().current_child = node:private().current_child + 1 end
 		until (result ~= false) or (node:private().current_child > #node.children)
 
 		return result
@@ -174,30 +216,11 @@ Tactree.Leaf 'Selector'
 
 Tactree.Leaf 'Inverter'
 {
-	start = function(node)
-		node.children[1]:start()
-	end,
-	tick = function(node, ...)
+	function(node, ...)
 		local result = node.children[1]:update(...)
 
-		if type(result) == 'boolean' then return not result end
+		if result ~= nil then return not result end
 	end
 }
 
---[[
-	Example usage
-	-------------
-
-	Tactree.Leaf 'Find nearest object' { function (node) ... end }
-	Tactree.Leaf 'Pick up object' { function (node) ... end}
-	Tactree.Leaf 'Move' { function (node) return node.data.creature:move(node.data.tx, node.data.ty, dt) end }
-	Tactree.Composite 'Pick up nearest object' 'Sequence' { 'Find nearest object', 'Move', 'Pick up object' }
-
-	local tr = Tactree.Tree 'Pick up nearest object'
-
-	tr:start{ ... } ( or, if you already have a table, tr:start(existing_table) )
-
-	t:update()
-]]--
-
 return Tactree
\ No newline at end of file