diff --git a/Project.toml b/Project.toml
index 2dc8c03..a5146a3 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "MicrobeAgents"
 uuid = "b17a4bac-8667-4a2d-84f7-1883ae0b8dbb"
 authors = ["Riccardo Foffi <rfoffi@ethz.ch> and contributors"]
-version = "0.4.1"
+version = "0.4.2"
 
 [deps]
 Agents = "46ada45e-f475-11e8-01d0-f70cc89e6671"
@@ -9,9 +9,9 @@ Autocorrelations = "b9118d5e-f165-4cbd-b2ae-b030566b7b26"
 DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"
 GeometryBasics = "5c1252a2-5f33-56bf-86c9-59e7332b4326"
+LightSumTypes = "f56206fc-af4c-5561-a72a-43fe2ca5a923"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MeanSquaredDisplacement = "13c93d70-909c-440c-af92-39d48ffa2ba2"
-MixedStructTypes = "3d69f371-6fa5-5add-b11c-3293622cad62"
 Quaternions = "94ee1d12-ae83-5a48-8b1c-48b8ff168ae0"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
@@ -23,8 +23,8 @@ Autocorrelations = "0.1"
 DataFrames = "1"
 Distributions = "0.25"
 GeometryBasics = "0.4"
+LightSumTypes = "4"
 MeanSquaredDisplacement = "0.2"
-MixedStructTypes = "0.2"
 Quaternions = "0.7"
 StaticArrays = "1"
 StatsBase = "0.34"
diff --git a/benchmark/benchmarks_0.4.2.md b/benchmark/benchmarks_0.4.2.md
new file mode 100644
index 0000000..588f01a
--- /dev/null
+++ b/benchmark/benchmarks_0.4.2.md
@@ -0,0 +1,20 @@
+# MicrobeAgents.jl benchmarks - 0.4.2 
+
+## Simple stepping
+Type             | Time (μs)        | Allocs           | Memory          
+ --- | --- | --- | --- 
+Microbe{1}       | 5.23e-01         | 1.10e+01         | 1.79e+02        
+Microbe{2}       | 6.60e-01         | 1.50e+01         | 3.07e+02        
+Microbe{3}       | 7.39e-01         | 1.50e+01         | 3.07e+02        
+BrownBerg{1}     | 6.13e-01         | 1.70e+01         | 7.55e+02        
+BrownBerg{2}     | 7.35e-01         | 2.10e+01         | 9.79e+02        
+BrownBerg{3}     | 8.29e-01         | 2.10e+01         | 1.08e+03        
+Brumley{1}       | 6.11e-01         | 1.65e+01         | 7.47e+02        
+Brumley{2}       | 7.55e-01         | 2.05e+01         | 9.71e+02        
+Brumley{3}       | 8.49e-01         | 2.05e+01         | 1.07e+03        
+Celani{1}        | 5.47e-01         | 1.30e+01         | 3.71e+02        
+Celani{2}        | 7.36e-01         | 1.70e+01         | 5.31e+02        
+Celani{3}        | 8.00e-01         | 1.70e+01         | 5.63e+02        
+SonMenolascina{1} | 6.65e-01         | 1.60e+01         | 7.39e+02        
+SonMenolascina{2} | 8.02e-01         | 2.00e+01         | 9.64e+02        
+SonMenolascina{3} | 8.90e-01         | 2.00e+01         | 1.06e+03        
diff --git a/src/MicrobeAgents.jl b/src/MicrobeAgents.jl
index 511dc81..b79c24e 100644
--- a/src/MicrobeAgents.jl
+++ b/src/MicrobeAgents.jl
@@ -7,8 +7,8 @@ export add_agent!, add_agent_own_pos!
 export move_agent!, walk!, run!
 
 using Distributions
+using LightSumTypes
 using LinearAlgebra
-using MixedStructTypes
 using Random
 using Quaternions
 using StaticArrays
diff --git a/src/microbe_step.jl b/src/microbe_step.jl
index 6cb2e9c..e62ad2c 100644
--- a/src/microbe_step.jl
+++ b/src/microbe_step.jl
@@ -24,7 +24,7 @@ function microbe_step!(microbe::AbstractMicrobe, model::AgentBasedModel)
         # if the new motile state is a TurnState with duration 0
         # immediately turn and transition to another state
         new_motilestate = motilestate(microbe)
-        if kindof(new_motilestate) === :TurnState && iszero(duration(new_motilestate))
+        if variantof(new_motilestate) === TurnState && iszero(duration(new_motilestate))
             turn!(microbe, model)
             update_motilestate!(microbe, model)
         end
@@ -53,7 +53,7 @@ function microbe_pathfinder_step!(microbe::AbstractMicrobe, model::AgentBasedMod
         # if the new motile state is a TurnState with duration 0
         # immediately turn and transition to another state
         new_motilestate = motilestate(microbe)
-        if kindof(new_motilestate) === :TurnState && iszero(duration(new_motilestate))
+        if variantof(new_motilestate) === TurnState && iszero(duration(new_motilestate))
             turn!(microbe, model)
             update_motilestate!(microbe, model)
         end
diff --git a/src/motility.jl b/src/motility.jl
index aa592cc..98bb260 100644
--- a/src/motility.jl
+++ b/src/motility.jl
@@ -5,28 +5,30 @@ export motilepattern, motilestate, state, states, transition_weights
 export duration, speed, polar, azimuthal
 export Arccos # from Agents
 
-@compact_structs MotileState begin
-    @kwdef struct RunState
-        duration
-        speed
-        polar = nothing
-        azimuthal = nothing
-    end
-    @kwdef struct TurnState
-        duration
-        speed = [zero(duration)]
-        polar
-        azimuthal
-    end
-end
 
-function biased(s::MotileState)
-    if kindof(s) === :RunState
-        return true
-    else # TurnState
-        return false
-    end
+struct RunState
+    duration
+    speed
+    polar
+    azimuthal
 end
+struct TurnState
+    duration
+    speed
+    polar
+    azimuthal
+end
+@sumtype MotileState(RunState, TurnState)
+function RunState(; duration, speed, polar=nothing, azimuthal=nothing)
+    MotileState(RunState(duration, speed, polar, azimuthal))
+end
+function TurnState(; duration, speed=[zero(duration)], polar, azimuthal)
+    MotileState(TurnState(duration, speed, polar, azimuthal))
+end
+
+biased(s::MotileState) = biased(variant(s))
+biased(::RunState) = true
+biased(::TurnState) = false
 
 # Base motile states
 Run(duration::Real, speed) = RunState(; duration, speed)