Hakkaa Päälle: Wargames Rules for the Age of Gustavus Adolphus, Tilly, and Koniecpolski

From the game's introduction:

"HP is a combination of rule changes, additions and army lists to allow the Gå På rules to be used for the first half of the 17th century. The focus is on the Thirty Years War, but it is certainly possible to use them for other conflicts as well. Examples of these include, but are not limited to: the English Civil War and the wars between Sweden and Poland. I have intentionally left the late 17th century out, as I feel this period is better covered by the standard rules.

"My ambition has been to include enough new/changed elements to produce the right "period feel". The game should not feel like a WSS game with different figures. I have tried to do it as I haven‟t found a set of rules that deal with the 30YW in a way I like, and because I felt that Gå På actually could be used to cover the period - although with some changes needed.

"Because of this I have decided to change some of the unit type names, and create new ones as well. My hope is that this doesn‟t create too much confusion, but instead generates more period feel.

"In the 17th century units tended to use deeper formations. The musketeers had a slower rate of fire and the socket bayonet arrived only towards the end of the period. This means they will have to be protected by pike-armed friends to a much larger degree."