diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 920eeb6..8f18c2e 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -14,7 +14,7 @@ Metrics/AbcSize:
 # Offense count: 2
 # Configuration parameters: CountComments, CountAsOne.
 Metrics/ClassLength:
-  Max: 208
+  Max: 217
 
 # Offense count: 3
 # Configuration parameters: AllowedMethods, AllowedPatterns.
diff --git a/lib/glug/layer.rb b/lib/glug/layer.rb
index 39ff310..d98bedf 100644
--- a/lib/glug/layer.rb
+++ b/lib/glug/layer.rb
@@ -82,7 +82,23 @@ def initialize(stylesheet, args = {})
     end
 
     def dsl_eval(&block)
+      # Copy ivars from stylesheet DSL to layer DSL (before eval)
+      style_dsl = @stylesheet.dsl
+      style_dsl.instance_variables.each do |ivar|
+        next if ivar.to_s.start_with?('@__') # skip internal ivars
+
+        @dsl.instance_variable_set(ivar, style_dsl.instance_variable_get(ivar))
+      end
+
+      # Run the layer evaluation
       @dsl.instance_eval(&block)
+
+      # Copy ivars back to stylesheet DSL (after eval)
+      @dsl.instance_variables.each do |ivar|
+        next if ivar.to_s.start_with?('@__') # skip internal ivars
+
+        style_dsl.instance_variable_set(ivar, @dsl.instance_variable_get(ivar))
+      end
     end
 
     # Handle all missing 'method' calls
diff --git a/lib/glug/stylesheet.rb b/lib/glug/stylesheet.rb
index 8223f19..0b5a334 100644
--- a/lib/glug/stylesheet.rb
+++ b/lib/glug/stylesheet.rb
@@ -3,7 +3,7 @@
 module Glug
   # the main document object
   class Stylesheet
-    attr_accessor :sources, :kv, :base_dir, :params
+    attr_accessor :sources, :kv, :base_dir, :params, :dsl
 
     def initialize(base_dir: nil, params: nil, &block)
       @sources = {}
diff --git a/lib/glug/stylesheet_dsl.rb b/lib/glug/stylesheet_dsl.rb
index 12361f5..9590090 100644
--- a/lib/glug/stylesheet_dsl.rb
+++ b/lib/glug/stylesheet_dsl.rb
@@ -26,7 +26,11 @@ def respond_to_missing?(*)
 
     # Set a property, e.g. 'bearing 29'
     def method_missing(method_sym, *args)
-      @__impl.add_property(method_sym, *args)
+      if Layer::EXPRESSIONS.include?(method_sym)
+        Condition.new.from_list(method_sym, args)
+      else
+        @__impl.add_property(method_sym, *args)
+      end
     end
   end
 end
diff --git a/spec/fixtures/expression_ivars.glug b/spec/fixtures/expression_ivars.glug
new file mode 100644
index 0000000..ea17541
--- /dev/null
+++ b/spec/fixtures/expression_ivars.glug
@@ -0,0 +1,12 @@
+version 8
+name 'Expression ivars test'
+source :shortbread, type: 'vector', url: 'https://vector.openstreetmap.org/shortbread_v1/tilejson.json'
+
+# Expression assigned to ivar at stylesheet level
+@my_halo = rgba(255, 255, 255, 0.8)
+@my_color = rgb(100, 200, 50)
+
+layer(:labels, zoom: 5.., source: :shortbread) do
+  text_halo_color @my_halo
+  text_color @my_color
+end
diff --git a/spec/fixtures/expression_ivars.json b/spec/fixtures/expression_ivars.json
new file mode 100644
index 0000000..ccf97c9
--- /dev/null
+++ b/spec/fixtures/expression_ivars.json
@@ -0,0 +1,23 @@
+{
+  "version":8,
+  "name":"Expression ivars test",
+  "sources":{
+    "shortbread":{
+      "type":"vector",
+      "url":"https://vector.openstreetmap.org/shortbread_v1/tilejson.json"
+    }
+  },
+  "layers":[
+    {
+      "paint":{
+        "text-halo-color":["rgba",255,255,255,0.8],
+        "text-color":["rgb",100,200,50]
+      },
+      "source":"shortbread",
+      "id":"labels",
+      "source-layer":"labels",
+      "type":"symbol",
+      "minzoom":5
+    }
+  ]
+}
\ No newline at end of file
diff --git a/spec/fixtures/ivars.glug b/spec/fixtures/ivars.glug
new file mode 100644
index 0000000..4f90f91
--- /dev/null
+++ b/spec/fixtures/ivars.glug
@@ -0,0 +1,23 @@
+version 8
+name 'My first stylesheet'
+source :shortbread, type: 'vector', url: 'https://vector.openstreetmap.org/shortbread_v1/tilejson.json'
+
+# set at stylesheet level
+@width = 6
+
+layer(:roads, zoom: 10..13, source: :shortbread) do
+  # get at layer level
+  line_width @width
+  line_color 0x888888
+end
+
+layer(:water, source: :shortbread) do
+  # set at layer level
+  @water = 'blue'
+  fill_color @water
+end
+
+layer(:water_line, source: :shortbread) do
+  # get from other layer
+  fill_color @water
+end
diff --git a/spec/fixtures/ivars.json b/spec/fixtures/ivars.json
new file mode 100644
index 0000000..14669b8
--- /dev/null
+++ b/spec/fixtures/ivars.json
@@ -0,0 +1,35 @@
+{
+  "version":8,
+  "name":"My first stylesheet",
+  "sources":{
+    "shortbread":{
+      "type":"vector",
+      "url":"https://vector.openstreetmap.org/shortbread_v1/tilejson.json"
+    }
+  },
+  "layers":[
+    {
+      "paint":{"line-width":6,"line-color":"#888888"},
+      "source":"shortbread",
+      "id":"roads",
+      "source-layer":"roads",
+      "type":"line",
+      "minzoom":10,
+      "maxzoom":13
+    },
+    {
+      "paint":{"fill-color":"blue"},
+      "source":"shortbread",
+      "id":"water",
+      "source-layer":"water",
+      "type":"fill"
+    },
+    {
+      "paint":{"fill-color":"blue"},
+      "source":"shortbread",
+      "id":"water_line",
+      "source-layer":"water_line",
+      "type":"fill"
+    }
+  ]
+}
diff --git a/spec/fixtures/ivars_with_include.glug b/spec/fixtures/ivars_with_include.glug
new file mode 100644
index 0000000..4b612a8
--- /dev/null
+++ b/spec/fixtures/ivars_with_include.glug
@@ -0,0 +1,8 @@
+version 8
+name 'My first stylesheet'
+source :shortbread, type: 'vector', url: 'https://vector.openstreetmap.org/shortbread_v1/tilejson.json'
+
+# set at stylesheet level
+@width = 6
+
+include_file 'ivars_with_include_sub.glug'
diff --git a/spec/fixtures/ivars_with_include.json b/spec/fixtures/ivars_with_include.json
new file mode 100644
index 0000000..62083cf
--- /dev/null
+++ b/spec/fixtures/ivars_with_include.json
@@ -0,0 +1,21 @@
+{
+  "version":8,
+  "name":"My first stylesheet",
+  "sources":{
+    "shortbread":{
+      "type":"vector",
+      "url":"https://vector.openstreetmap.org/shortbread_v1/tilejson.json"
+    }
+  },
+  "layers":[
+    {
+      "paint":{"line-width":6,"line-color":"#888888"},
+      "source":"shortbread",
+      "id":"roads",
+      "source-layer":"roads",
+      "type":"line",
+      "minzoom":10,
+      "maxzoom":13
+    }
+  ]
+}
diff --git a/spec/fixtures/ivars_with_include_sub.glug b/spec/fixtures/ivars_with_include_sub.glug
new file mode 100644
index 0000000..21c6a99
--- /dev/null
+++ b/spec/fixtures/ivars_with_include_sub.glug
@@ -0,0 +1,4 @@
+layer(:roads, zoom: 10..13, source: :shortbread) do
+  line_width @width
+  line_color 0x888888
+end
diff --git a/spec/lib/glug/stylesheet_spec.rb b/spec/lib/glug/stylesheet_spec.rb
index c3654fc..f25811e 100644
--- a/spec/lib/glug/stylesheet_spec.rb
+++ b/spec/lib/glug/stylesheet_spec.rb
@@ -86,5 +86,32 @@
       output = File.read(File.join(fixture_dir, 'basic_with_include.json'))
       expect(stylesheet.to_json).to eql(output.strip)
     end
+
+    it 'sets and gets instance variables across the whole stylesheet' do
+      glug = File.read(File.join(fixture_dir, 'ivars.glug'))
+      stylesheet = described_class.new(base_dir: fixture_dir) do
+        instance_eval(glug)
+      end
+      output = File.read(File.join(fixture_dir, 'ivars.json'))
+      expect(stylesheet.to_json).to eql(output.strip)
+    end
+
+    it 'sets and gets instance variables across included stylesheets' do
+      glug = File.read(File.join(fixture_dir, 'ivars_with_include.glug'))
+      stylesheet = described_class.new(base_dir: fixture_dir) do
+        instance_eval(glug)
+      end
+      output = File.read(File.join(fixture_dir, 'ivars_with_include.json'))
+      expect(stylesheet.to_json).to eql(output.strip)
+    end
+
+    it 'stores expressions in ivars at stylesheet level' do
+      glug = File.read(File.join(fixture_dir, 'expression_ivars.glug'))
+      stylesheet = described_class.new(base_dir: fixture_dir) do
+        instance_eval(glug)
+      end
+      output = File.read(File.join(fixture_dir, 'expression_ivars.json'))
+      expect(stylesheet.to_json).to eql(output.strip)
+    end
   end
 end