progression={
 -- level 1
 ruleset:new(1,5,1,9,0,nil,1), -- by test: always winnable
 -- level 2
 ruleset:new(2,5,2,9,0,nil,2), -- by test: always winnable
 -- level 3
 ruleset:new(3,7,2,9,8),  -- by test: always winnable
 -- level 4 (first challenging)
 ruleset:new(4,9,3,9,16, "l4"),
 -- level 5 
 ruleset:new(5,9,3,11,18, "l5"),
 -- fortune's foundation
 ruleset:new(6,11,4,13,22,"ff"),
 -- harder than fortune's foundation
 ruleset:new(7,11,5,10,25,"l7")
}