to build a turret, click the second button from the right and than where to place it to upgrade a turret, select a turret of your choice and than one of the upgrades at the bottom left corner
This is the first time I created a Tower Defense game, so don't mind any balance-issues xd Created in 8hours - it has 3 different turrets and 25 waves Music by Keegs "m" to mute/unmute
