Charge Yr Pikes is a set of free wargames rules for the English Civil War. The authors write:
This set of rules is considerably modified from the first edition, which was in turn a modified version of CAVALIERS AND ROUNDHEADS’, by Gygax & Perren. These modifications were based on general dissatisfaction with the parts of the first edition that contrasted most with the “Brom Standard” rules which were introduced to our club by Larry Brom. The later editions (3rd, 4th and this one) are merely attempts to “fine-tune” the second edition.