diff --git a/anselme/ast/Closure.lua b/anselme/ast/Closure.lua
index 15772f9..5a1d2bc 100644
--- a/anselme/ast/Closure.lua
+++ b/anselme/ast/Closure.lua
@@ -19,6 +19,7 @@ Closure = Runtime(Overloadable) {
 		-- to allow future define in the function (fn.:var = "foo")
 		state.scope:push()
 		self.scope = state.scope:capture()
+		state.scope:define(ast.Symbol:new("_calling_environment"), self.scope)
 		state.scope:pop()
 	end,
 
@@ -38,20 +39,33 @@ Closure = Runtime(Overloadable) {
 		return self.func.parameters:format(state)
 	end,
 	call_dispatched = function(self, state, args)
+		local calling_environment = state.scope:capture()
 		state.scope:push(self.scope)
+		state.scope:set(ast.Identifier:new("_calling_environment"), calling_environment)
 		local exp = self.func:call_dispatched(state, args)
 		state.scope:pop()
 		return exp
 	end,
 	resume = function(self, state, target)
 		if self.func.parameters.min_arity > 0 then error("can't resume function with parameters") end
+		local calling_environment = state.scope:capture()
 		state.scope:push(self.scope)
+		state.scope:set(ast.Identifier:new("_calling_environment"), calling_environment)
 		resume_manager:push(state, target)
 		local exp = self.func:call(state, ast.ArgumentTuple:new())
 		resume_manager:pop(state)
 		state.scope:pop()
 		return exp
 	end,
+	get_level = function(self, state, level) -- TODO make generic to all calls? only closures?
+		local env = state.scope:capture()
+		while level > 0 do
+			assert(env:defined(state, ast.Identifier:new("_calling_environment")))
+			env = env:get(state, ast.Identifier:new("_calling_environment"))
+			level = level - 1
+		end
+		return env
+	end
 }
 
 package.loaded[...] = Closure
diff --git a/anselme/ast/Environment.lua b/anselme/ast/Environment.lua
index 2986299..891a671 100644
--- a/anselme/ast/Environment.lua
+++ b/anselme/ast/Environment.lua
@@ -2,7 +2,7 @@ local ast = require("anselme.ast")
 
 local operator_priority = require("anselme.common").operator_priority
 
-local Branched, ArgumentTuple, Overload, Overloadable, Table, Call, ParameterTuple, Function, FunctionParameter, Identifier
+local Branched, ArgumentTuple, Overload, Overloadable, Table
 
 local VariableMetadata = ast.abstract.Runtime {
 	type = "variable metadata",
@@ -180,6 +180,7 @@ local Environment = ast.abstract.Runtime {
 	end,
 
 	-- returns a list {[symbol]=val,...} of all exported variables (evaluated) in the current strict layer
+	-- TODO currently unused
 	list_exported = function(self, state)
 		assert(self.export, "not an export scope layer")
 		local r = {}
@@ -219,6 +220,6 @@ local Environment = ast.abstract.Runtime {
 }
 
 package.loaded[...] = Environment
-Branched, ArgumentTuple, Overload, Overloadable, Table, Call, ParameterTuple, Function, FunctionParameter, Identifier = ast.Branched, ast.ArgumentTuple, ast.Overload, ast.abstract.Overloadable, ast.Table, ast.Call, ast.ParameterTuple, ast.Function, ast.FunctionParameter, ast.Identifier
+Branched, ArgumentTuple, Overload, Overloadable, Table = ast.Branched, ast.ArgumentTuple, ast.Overload, ast.abstract.Overloadable, ast.Table
 
 return Environment
diff --git a/anselme/stdlib/boolean.lua b/anselme/stdlib/boolean.lua
index b797716..03fb242 100644
--- a/anselme/stdlib/boolean.lua
+++ b/anselme/stdlib/boolean.lua
@@ -6,13 +6,20 @@ return {
 		"_==_", "(a, b)",
 		function(state, a, b)
 			if a.mutable ~= b.mutable then return Boolean:new(false)
-			elseif a.mutable then
-				return Boolean:new(a == b)
 			else
 				return Boolean:new(a:hash() == b:hash())
 			end
 		end
 	},
+	{
+		"_!=_", "(a, b)",
+		function(state, a, b)
+			if a.mutable ~= b.mutable then return Boolean:new(true)
+			else
+				return Boolean:new(a:hash() ~= b:hash())
+			end
+		end
+	},
 	{
 		"!_", "(a)",
 		function(state, a)
diff --git a/anselme/stdlib/checkpoint.lua b/anselme/stdlib/checkpoint.lua
index a57af8f..95c53ee 100644
--- a/anselme/stdlib/checkpoint.lua
+++ b/anselme/stdlib/checkpoint.lua
@@ -1,5 +1,5 @@
 local ast = require("anselme.ast")
-local ArgumentTuple = ast.ArgumentTuple
+local ArgumentTuple, Boolean = ast.ArgumentTuple, ast.Boolean
 
 local resume_manager = require("anselme.state.resume_manager")
 
@@ -18,5 +18,33 @@ return {
 		function(state, anchor, quote)
 			return quote:call(state, ArgumentTuple:new())
 		end
-	}
+	},
+	{
+		"resume", "(function::closure, anchor::anchor)",
+		function(state, func, anchor)
+			return func:resume(state, anchor)
+		end
+	},
+	{
+		"resuming", "()",
+		function(state)
+			return Boolean:new(resume_manager:resuming(state))
+		end
+	},
+	{
+		"resuming", "(level::number)",
+		function(state, level)
+			local env = ast.Closure:get_level(state, level:to_lua(state))
+			state.scope:push(env)
+			local r = Boolean:new(resume_manager:resuming(state))
+			state.scope:pop()
+			return r
+		end
+	},
+	{
+		"resume target", "()",
+		function(state)
+			return resume_manager:get(state)
+		end
+	},
 }
diff --git a/anselme/stdlib/init.lua b/anselme/stdlib/init.lua
index 4efbac9..9b3d8de 100644
--- a/anselme/stdlib/init.lua
+++ b/anselme/stdlib/init.lua
@@ -20,8 +20,7 @@ return function(main_state)
 		"type_check"
 	})
 
-	local boot = parser(require("anselme.stdlib.boot_script"), "boot.ans")
-	boot:eval(main_state)
+	parser(require("anselme.stdlib.boot_script"), "boot.ans"):eval(main_state)
 
 	load(main_state, {
 		"number",
@@ -32,4 +31,6 @@ return function(main_state)
 		"checkpoint",
 		"persist",
 	})
+
+	parser(require("anselme.stdlib.script_script"), "script.ans"):eval(main_state)
 end
diff --git a/anselme/stdlib/script_script.lua b/anselme/stdlib/script_script.lua
new file mode 100644
index 0000000..8b08bc6
--- /dev/null
+++ b/anselme/stdlib/script_script.lua
@@ -0,0 +1,57 @@
+return [[
+:@script = $(name, fn)
+	:&current checkpoint => "{name}.checkpoint"!persist(false)
+	:&reached => "{name}.reached"!persist(*{})
+	:resumed from = ()
+
+	fn.:check = $(anchor::anchor)
+		reached(anchor) = (reached(anchor) | 0) + 1
+	fn.:checkpoint = $(anchor::anchor)
+		current checkpoint = anchor
+		resumed from != anchor ~
+			reached(anchor) = (reached(anchor) | 0) + 1
+	fn.:checkpoint = $(anchor::anchor, on resume::function)
+		current checkpoint = anchor
+		resumed from == anchor | resuming(1) ~
+			on resume!
+		~
+			reached(anchor) = (reached(anchor) | 0) + 1
+
+	:f = $
+		current checkpoint ~
+			resumed from = current checkpoint
+			fn!resume(current checkpoint)
+		~
+			resumed from = ()
+			fn!
+		run += 1
+	f.:&run => "{name}.run"!persist(0)
+
+	f!type("script")
+
+:is script = is("script")
+
+:@$_!(s::is script)
+	s!value!
+
+:@$_._(s::is script, k::string)
+	:v = s!value
+	v.fn!has upvalue(k) ~
+		@v.fn.(k)
+	~
+		@v.(k)
+
+:@$_._(s::is script, k::string) = val
+	:v = s!value
+	v.fn!has upvalue(k) ~
+		v.fn.(k) = val
+	~
+		v.(k) = val
+
+:@$from(s::is script, a::anchor)
+	s.current checkpoint = a
+	@s!
+:@$from(s::is script)
+	s.current checkpoint = ()
+	@s!
+]]
\ No newline at end of file