diff --git a/src/actions.jl b/src/actions.jl
index 33006bd..5f30c21 100644
--- a/src/actions.jl
+++ b/src/actions.jl
@@ -24,3 +24,9 @@ const TURN_LEFT = TurnLeft()
 (x::TurnLeft)(::Up) = LEFT
 (x::TurnLeft)(::Right) = UP
 (x::TurnLeft)(::Down) = RIGHT
+
+struct Pickup <: AbstractGridWorldAction end
+const PICK_UP = Pickup()
+
+struct Drop <: AbstractGridWorldAction end
+const DROP = Drop()
diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index e3bbed6..8228c96 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -6,7 +6,6 @@ mutable struct DoorKey{W<:GridWorldBase} <: AbstractGridWorld
     world::W
     agent_pos::CartesianIndex{2}
     agent::Agent
-    has_key::Bool
 end
 
 function DoorKey(;n=8, agent_start_pos=CartesianIndex(2,2), rng=Random.GLOBAL_RNG)
@@ -32,7 +31,7 @@ function DoorKey(;n=8, agent_start_pos=CartesianIndex(2,2), rng=Random.GLOBAL_RN
     world[EMPTY, key_pos] = false
     world[Key(:yellow), key_pos] = true
 
-    DoorKey(world, agent_start_pos, Agent(dir=RIGHT),false)
+    DoorKey(world, agent_start_pos, Agent(;dir=RIGHT))
 end
 
 function (w::DoorKey)(::MoveForward)
@@ -40,14 +39,15 @@ function (w::DoorKey)(::MoveForward)
     dest = dir(w.agent_pos)
 
     if w.world[Key(:yellow), dest]
-        w.has_key = true
-        w.world[Key(:yellow), dest] = false
-        w.world[EMPTY, dest] = true
+        if PICK_UP(w.agent, Key(:yellow))
+            w.world[Key(:yellow), dest] = false
+            w.world[EMPTY, dest] = true
+        end
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.has_key
-        w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && !w.has_key
+    elseif w.world[Door(:yellow), dest] && w.agent.inventory !== Key(:yellow)
         nothing
+    elseif w.world[Door(:yellow), dest] && w.agent.inventory === Key(:yellow)
+        w.agent_pos = dest
     elseif dest ∈ CartesianIndices((size(w.world, 2), size(w.world, 3))) && !w.world[WALL,dest]
         w.agent_pos = dest
     end
diff --git a/src/objects.jl b/src/objects.jl
index bf7e6b9..1fb947e 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -50,17 +50,22 @@ const OBSTACLE = Obstacle()
 Base.convert(::Type{Char}, ::Obstacle) = '⊗'
 get_color(::Obstacle) = :blue    
 
+#####
+# Agent
+#####
+
 Base.@kwdef mutable struct Agent <: AbstractObject
     color::Symbol=:red
     dir::LRUD
+    inventory::Union{Nothing, AbstractObject, Vector}=nothing
 end
 
 function Base.convert(::Type{Char}, a::Agent)
-    if        a.dir === UP
+    if     a.dir === UP
         '↑'
-    elseif  a.dir === DOWN
+    elseif a.dir === DOWN
         '↓'
-    elseif  a.dir === LEFT
+    elseif a.dir === LEFT
         '←'
     elseif a.dir === RIGHT
         '→'
@@ -70,3 +75,51 @@ end
 get_color(a::Agent) = a.color
 get_dir(a::Agent) = a.dir
 set_dir!(a::Agent, d) = a.dir = d
+
+struct Transportable end
+struct Nontransportable end
+const TRANSPORTABLE = Transportable()
+const NONTRANSPORTABLE = Nontransportable()
+istransportable(::Type{<:Key}) = TRANSPORTABLE
+istransportable(::Type{Gem}) = TRANSPORTABLE
+istransportable(x::AbstractObject) = istransportable(typeof(x))
+
+(x::Pickup)(a::Agent, o) = x(istransportable(o), a, o)
+
+function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 
+    if isnothing(a.inventory)
+        a.inventory = o
+        true
+    elseif a.inventory isa Vector
+        i = findfirst(isnothing, a.v)
+        if isnothing(i)
+            false
+        else
+            a.inventory[i] = o
+            true
+        end
+    else
+        false
+    end
+end
+
+function (::Drop)(a::Agent)
+    if isnothing(a.inventory)
+        nothing
+    elseif a.inventory isa AbstractObject
+        x = a.inventory
+        a.inventory = nothing
+        x
+    elseif a.inventory isa Vector
+        i = findlast(x -> x isa AbstractObject, a.inventory)
+        if isnothing(i)
+            nothing
+        else
+            x = a.inventory[i]
+            a.inventory[i] = nothing
+            x
+        end
+    else
+        @error "unknown inventory type $(a.inventory)"
+    end
+end