diff --git a/spec/entitas/events_spec.cr b/spec/entitas/events_spec.cr
index cdfd9c2..c8cb89f 100644
--- a/spec/entitas/events_spec.cr
+++ b/spec/entitas/events_spec.cr
@@ -23,7 +23,7 @@ private class RemoveEventTest
 
   property listener : Test4Entity
   property contexts : Contexts
-  property remove_comp_when_empty : Bool
+  property? remove_comp_when_empty : Bool
   property value : String? = nil
 
   def initialize(@contexts, @remove_comp_when_empty)
@@ -37,13 +37,13 @@ private class RemoveEventTest
 
   def on_standard_event(entity, component : StandardEvent)
     # logger.warn { "on_standard_event" }
-    @listener.remove_any_standard_event_listener(self, remove_comp_when_empty)
+    @listener.remove_any_standard_event_listener(self, remove_comp_when_empty?)
     @value = component.value
   end
 
   def on_flag_entity_event(entity, component : FlagEntityEvent)
     # logger.warn { "on_flag_entity_event" }
-    listener.remove_flag_entity_event_listener(self, remove_comp_when_empty)
+    listener.remove_flag_entity_event_listener(self, remove_comp_when_empty?)
     @value = "true"
   end
 end
diff --git a/src/entitas/collector.cr b/src/entitas/collector.cr
index d012bbc..436730e 100644
--- a/src/entitas/collector.cr
+++ b/src/entitas/collector.cr
@@ -91,7 +91,7 @@ module Entitas
       self.entities.size
     end
 
-    def each
+    def each(& : TEntity ->)
       self.entities.each do |entity|
         yield entity
       end
diff --git a/src/entitas/contexts.cr b/src/entitas/contexts.cr
index 2ed3bdd..1215dcb 100644
--- a/src/entitas/contexts.cr
+++ b/src/entitas/contexts.cr
@@ -23,7 +23,7 @@ class Entitas::Contexts
     self.all_contexts.each &.reset
   end
 
-  def each
+  def each(& : Entitas::IContext? ->)
     self.all_contexts.each do |ctx|
       yield ctx
     end
diff --git a/src/entitas/controller.cr b/src/entitas/controller.cr
index 7db235b..d21ad3a 100644
--- a/src/entitas/controller.cr
+++ b/src/entitas/controller.cr
@@ -12,7 +12,7 @@ module Entitas
 
     # Will allow you to interact with the returned `Contexts` with a `Mutex` lock
     # preventing `#update` from being called in another thread
-    def with_contexts
+    def with_contexts(& : Entitas::Contexts ->)
       self.synchronize do
         yield self.contexts
       end
@@ -23,10 +23,11 @@ module Entitas
     end
 
     def find_systems(klass : Class) : Array(Entitas::System)
-      if self.systems.nil?
+      sys = self.systems
+      if sys.nil?
         Array(Entitas::System).new
       else
-        self.systems.not_nil!.find_systems(klass)
+        sys.find_systems(klass)
       end
     end
 
diff --git a/src/entitas/interfaces/i_component.cr b/src/entitas/interfaces/i_component.cr
index 4c1be33..e5ba8c8 100644
--- a/src/entitas/interfaces/i_component.cr
+++ b/src/entitas/interfaces/i_component.cr
@@ -2,7 +2,7 @@ module Entitas::IComponent
   Log = ::Log.for(self)
 
   # Will return true if the class is a unique component for a context
-  abstract def is_unique? : Bool
+  abstract def unique? : Bool
   abstract def init(**args)
   abstract def reset
 
diff --git a/src/entitas/macros/component.cr b/src/entitas/macros/component.cr
index 250c9bd..a7b8cbf 100644
--- a/src/entitas/macros/component.cr
+++ b/src/entitas/macros/component.cr
@@ -133,7 +133,7 @@ module Entitas::IComponent
     def to_json(json : JSON::Builder)
       json.object do
         json.field "name", {{@type.id.stringify}}
-        json.field "unique", is_unique?
+        json.field "unique", unique?
         json.field("data") do
           json.object do
             {% for var_name in comp_variables.keys %}
@@ -206,31 +206,31 @@ module Entitas::IComponent
 
   # :nodoc:
   macro setup_unique
-    {% is_unique = @type.annotation(::Component::Unique) ? true : false %}
+    {% unique = @type.annotation(::Component::Unique) ? true : false %}
 
-    {% if flag?(:entitas_debug_generator) %}{% puts "  - setup_unique for #{@type.id} : #{is_unique}" %}{% end %}
+    {% if flag?(:entitas_debug_generator) %}{% puts "  - setup_unique for #{@type.id} : #{unique}" %}{% end %}
 
     # If the component has the unique annotation,
     #   set the class method to `true`
     # The framework will make sure that only one instance of a unique component can be present in your context
-    {% if is_unique %}
+    {% if unique %}
       # Will return true if the class is a unique component for a context
-      def is_unique? : Bool
+      def unique? : Bool
         true
       end
 
       # :ditto:
-      def self.is_unique? : Bool
+      def self.unique? : Bool
         true
       end
     {% else %}
       # Will return true if the class is a unique component for a context
-      def is_unique? : Bool
+      def unique? : Bool
         false
       end
 
       # :ditto:
-      def self.is_unique? : Bool
+      def self.unique? : Bool
         false
       end
     {% end %}
diff --git a/src/entitas/macros/events.cr b/src/entitas/macros/events.cr
index a87fabc..eedbe80 100644
--- a/src/entitas/macros/events.cr
+++ b/src/entitas/macros/events.cr
@@ -254,7 +254,7 @@ macro component_event(contexts, comp, target, _type = EventType::Added, priority
       end
 
       def remove_{{listener_component_meth_name.id}}(value : {{listener_module.id}}, remove_comp_when_empty = false)
-        {% if flag?(:entitas_enable_logging) %}Log.debug { "remove_{{listener_component_meth_name.id}} - remove_comp_when_empty: #{remove_comp_when_empty}, value: #{value}" }{% end %}
+        {% if flag?(:entitas_enable_logging) %}Log.debug { "remove_{{listener_component_meth_name.id}} - remove_comp_when_empty: #{remove_comp_when_empty?}, value: #{value}" }{% end %}
         %listeners = self.{{listener_component_meth_name.id}}.value
         %listeners.delete(value)
         if(remove_comp_when_empty && %listeners.empty?)
diff --git a/src/entitas/multi_reactive_system.cr b/src/entitas/multi_reactive_system.cr
index 1f41e57..c759724 100644
--- a/src/entitas/multi_reactive_system.cr
+++ b/src/entitas/multi_reactive_system.cr
@@ -15,7 +15,7 @@ module Entitas
     private property collected_buffer : Array(IEntity) = Array(IEntity).new
     private property buffer : Array(IEntity) = Array(IEntity).new
     private property to_string_cache : String? = nil
-    protected property _filter : Proc(IEntity, Bool) = ->(entity : IEntity) { true }
+    protected property _filter : Proc(IEntity, Bool) = ->(_entity : IEntity) { true }
 
     def initialize(@collectors : Array(ICollector)); end
 
diff --git a/src/entitas/reactive_system.cr b/src/entitas/reactive_system.cr
index f3a8e4e..da07f65 100644
--- a/src/entitas/reactive_system.cr
+++ b/src/entitas/reactive_system.cr
@@ -14,7 +14,7 @@ module Entitas
     private getter collector : ICollector
     private property buffer : Array(Entitas::IEntity) = Array(Entitas::IEntity).new
     private property to_string_cache : String? = nil
-    protected property _filter : Proc(Entitas::IEntity, Bool) = ->(entity : Entitas::IEntity) { true }
+    protected property _filter : Proc(Entitas::IEntity, Bool) = ->(_entity : Entitas::IEntity) { true }
 
     def initialize(@collector : ICollector); end