diff --git a/init.lua b/init.lua
index acfa3ba..a249bb9 100644
--- a/init.lua
+++ b/init.lua
@@ -3,23 +3,25 @@ local Nodes = {}
 
 local function NodeStart(node, args)
 	-- don't start again if started
-	if node.data then return end
+	if node._started then return end
 
-	node.data = node.parent and node.parent.data or args
+	node.data = node.parent and node.parent.data or args or node.data
 	node.data[node] = node.data[node] or {}
 	node:_start()
+
+	node._started = true
 end
 
-local function NodeUpdate(node)
-	-- don't tick if not started
-	if not node.data then return end
+local function NodeUpdate(node, ...)
+	-- automatically start if not started
+	if not node._started then NodeStart(node) end
 
-	local result = node:_tick()
+	local result = node:_tick(...)
 
 	if type(result) == 'boolean' then
 		node:_finish()
 
-		node.data = nil
+		node._started = false
 	end
 
 	return result
@@ -72,8 +74,10 @@ function Tactree.Composite(name)
 	end
 end
 
-function Tactree.Tree(name)
-	if not Nodes[name] then error('no such node \'' .. name .. '\'', 2) end
+local function tree_by_name(name, depth)
+	depth = depth or 2
+
+	if not Nodes[name] then error('no such node \'' .. name .. '\'', depth) end
 
 	local node = {}
 	node.children = {}
@@ -85,7 +89,7 @@ function Tactree.Tree(name)
 	-- find a way to prevent this?
 	if Nodes[name].children then
 		for _, child in ipairs(Nodes[name].children) do
-			local cn = Tactree.Tree(child)
+			local cn = tree_by_name(child, depth + 1)
 			cn.parent = node
 			table.insert(node.children, cn)
 		end
@@ -94,27 +98,59 @@ function Tactree.Tree(name)
 	return setmetatable(node, { __index = Nodes[name], __tostring = function() return name end })
 end
 
+function Tactree.Tree(name)
+	if not Nodes[name] then error('no such node \'' .. name .. '\'', 2) end
+
+	return function(children)
+		local node = {}
+		node.children = {}
+		node.start = NodeStart
+		node.update = NodeUpdate
+		node.private = NodePrivateData
+
+		-- add pre-defined children
+		if Nodes[name].children then
+			for _, child in ipairs(Nodes[name].children) do
+				local cn = tree_by_name(child, 3)
+				cn.parent = node
+				table.insert(node.children, cn)
+			end
+		end
+
+		-- add extra children from call
+		for _, child in ipairs(children) do
+			local cn
+			if type(child) == 'string' then
+				cn = tree_by_name(child, 3)
+			elseif type(child) == 'table' then
+				cn = child
+			else
+				error('invalid child type: \'' .. type(child) '\'', 3)
+			end
+
+			cn.parent = node
+			table.insert(node.children, cn)
+		end
+
+		return setmetatable(node, { __index = Nodes[name], __tostring = function() return name end })
+	end
+end
+
 Tactree.Leaf 'Sequence'
 {
 	start = function(node)
 		node:private().current_child = 1
-		node.children[node:private().current_child]:start()
 	end,
-	tick = function(node)
-		local result = node.children[node:private().current_child]:update()
-
-		if type(result) == 'boolean' then
+	tick = function(node, ...)
+		local result
+		repeat
+			result = node.children[node:private().current_child]:update(...)
 			if result then
-				if node:private().current_child == #node.children then
-					return true
-				else
-					node:private().current_child = node:private().current_child + 1
-					node.children[node:private().current_child]:start()
-				end
-			else
-				return false
+				node:private().current_child = node:private().current_child + 1
 			end
-		end
+		until (not result) or (node:private().current_child > #node.children)
+
+		return result
 	end
 }
 
@@ -122,23 +158,17 @@ Tactree.Leaf 'Selector'
 {
 	start = function(node)
 		node:private().current_child = 1
-		node.children[node:private().current_child]:start()
 	end,
-	tick = function(node)
-		local result = node.children[node:private().current_child]:update()
-
-		if type(result) == 'boolean' then
-			if not result then
-				if node:private().current_child == #node.children then
-					return false
-				else
-					node:private().current_child = node:private().current_child + 1
-					node.children[node:private().current_child]:start()
-				end
-			else
-				return true
+	tick = function(node, ...)
+		local result
+		repeat
+			result = node.children[node:private().current_child]:update(...)
+			if result then
+				node:private().current_child = node:private().current_child + 1
 			end
-		end
+		until (result ~= false) or (node:private().current_child > #node.children)
+
+		return result
 	end
 }
 
@@ -147,61 +177,13 @@ Tactree.Leaf 'Inverter'
 	start = function(node)
 		node.children[1]:start()
 	end,
-	tick = function(node)
-		local result = node.children[1]:update()
+	tick = function(node, ...)
+		local result = node.children[1]:update(...)
 
 		if type(result) == 'boolean' then return not result end
 	end
 }
 
-Tactree.Leaf 'RepeatUntilFail'
-{
-	start = function(node)
-		node.children[1]:start()
-	end,
-	tick = function(node)
-		local result = node.children[1]:update()
-
-		if type(result) == 'boolean' then
-			if not result then
-				return true
-			else
-				node.children[1]:start()
-			end
-		end
-	end
-}
-
-Tactree.Leaf 'RepeatUntilPass'
-{
-	start = function(node)
-		node.children[1]:start()
-	end,
-	tick = function(node)
-		local result = node.children[1]:update()
-
-		if type(result) == 'boolean' then
-			if result then
-				return true
-			else
-				node.children[1]:start()
-			end
-		end
-	end
-}
-
-Tactree.Leaf 'RepeatForever'
-{
-	start = function(node)
-		node.children[1]:start()
-	end,
-	tick = function(node)
-		local result = node.children[1]:update()
-
-		if type(result) == 'boolean' then node.children[1]:start() end
-	end
-}
-
 --[[
 	Example usage
 	-------------