Universal Features:
-Thick, moody fog and orange sky
-Purple clouds
-Per-biome water coloring and transparency
-Accurate bed and shulker coloring
-Old potion particle colors
-Clean block animations
-Improved block rotation
-Smaller chest inventory icons
-Textured piston arms
-Fiery launched fireworks
-Thematic boss bars
-Solid crosshairs
-Pumpkin Minecoins (and other minor menu changes)
-Deferred Renderer and Ray Tracing (RTX) support for sky and lighting
-Java and Console Aspects compatibility
-Music player integration
-Legacy Console UI panorama support

Halloween 2015 (Mash-up Style) Exclusive Features:
-Cohesive grass textures
-Unique stained glass textures
-Unique wool textures
-Transparent birch, spruce, and dark oak door textures
-Natural sculk and Nether stem animations
-Accurate Mash-up world panorama
-Accurate lapis item slot
-Deferred Renderer Only: Green-tinted block light

Halloween 2013 (Classic Style) Exclusive Features:
-Overhauled menus
-Monster-focused paintings
-Normal Minecraft music
-Spooky Nether panorama
-The following blocks are no longer animated:
  -Dandelion and poppy
  -Green and pink wools
  -Cactuses
  -Glowstone
  -Nether stems
  -Sculk and sculk vein