As lead level designer on Luna project, I’m creating some ‘tools’ (gameplay ideas list, ‘protocol’/workflow of level’s production…) in order to assure consistent levels, progress of difficulty…
To implement these tools, I try to draw inspiration from existing games, to analyze how they work, how they insert a new element, how they change parameters to change difficulty or give player time to understand and appropriate elements…
There are 5 worlds with each 10 levels. At every 5 levels there is a special mode (bowling, plant!..).
In the world 1, the first 4 levels are ‘introduction’ of basic elements (plant, sun, zombie, shovel), and level 5 is a special mode. At level 6 a new zombie (pole volting) appears with special feature : it can jump over an element. Level 7 is a test of the player : no new element but 2 waves of zombies attack : increase of difficulty on known elements. At level 8 : new zombie (buckethead, tougher) but a zombie (pole volting) removed : it’s a ‘tutorial’/assimilation level : player must now select his plants and understand the new zombie, so there is only one wave of zombies. Level 9 is a ‘synthesis’ of the world : all elements are here and there are 2 zombies waves. And level 10 (final level) is a synthesis during a special mode.
So we can see a pattern :
Level n1 : introduction of a new element
Level n2 : assimilation of the element (+ difficulty increases)
Level n3 : introduction of a new element (+ difficulty decreases)
Level n4 : synthesis (+ difficulty increases)
Level n5 : synthesis in special mode (fun time)