Major changes:

- The game is now fully narrated

• one voice for each major section of the game
  
• press 'P' to replay the poem inside a level
  
• narration volume slider added to the options menu
  

Minor changes:

-reworked stage-texts at beginning of each circle to sound more poetic
-reworked Virgil's comments, now they have a slightly more archaic tone
-A master volume slider added, it controls all music/sfx/narration sounds
-you can now hold down the undo button z, combine with holding shift to go back faster
-new intro screen on the first level
-improved tutorial texts on the first levels
-missing back-buttons added to the menu
-button for opening the main menu added to the top left corner (visible while movement indicator is)
-disabling particles now also disables block break effect
-the alternative movement-option is now reflected on the controls-menu
-option to limit FPS to 60 added to the main menu
-specified a max and min zoom level to prevent "infinite zoom bug"
-increased text contrast on snowy levels
-level numbers on level-select screen are now more visible
-level 17 fix: Prevented a water-walking solution when crossing Acheron
-level 71 fix: Changed the puzzle a bit and prevented an easier unintended solution
-the "additional data" setting now doesn't show debug-info unless in admin mode
-notifications now show up when trying to save/load while in Story mode, or while trying to enter a locked level
-the very last level now has a message to clearly signal the end of the game
-the tick on completed levels no longer obstructs the level numbers on the level select screen

Thanks to Dohi64 from the Puzzle Lovers steam group for many of the suggestions above!