for the lag issue guys just turn off shake from option and the lag will go i have no lagg at all atm and it work on firefox and google chrome as well :)
A few ideas:
1- about the warrior upgrade to knight you should make it more than 1 upgrade lets say:
warrior to knight gives bonus to attack power
warrior to soldier gives bonus to crit
warrior to paladin gives bonus to health and spd
warrior to elite knight gives bonus to all stats
and for mage the upgrades should be like this
mage to cleric give bonus to heal and dbl heal
mage to warlock gives a new skill blood thirst which absorbs enemy blood
mage to elite mage gives bonus to all stats includes the blood thirst skill
for rogue
rogue to assassin gives bonus to speed and posion and potency
rogue to elite rogue gives bonus to all stats
you put the bonus % and you should make all the upgrades units upgrades available for more bonus i.e
i could upgrade warrior to knight soldier paladin and elite warrior so on
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