I am currently working on the level design. I created a spreadsheet wich gives overview of the stages I created so far. To get a feeling for the game balance, every stage gets a number from 0 to 7 which represents the difficulty.
Here you can see a graph generated out of the sheet.
There are about 60 stages in 3 different settings I hope that will be enough for the final release.
But we will see…I hope to get some people who will test the game at our studio to find out how long they need to finish the whole game. I am targeting a gameplay length of about 3-4h.