Icetowers is a real-time simultaneous play game for 2-5 players involving stacking smaller pyramids on top of larger ones to control them. With the Icetowers set, you can play nearly any of the Icehouse games. (The color scheme of the Icetowers set -- purple, white, clear, and pale blue -- may cause some mild confusion for players reading rules that refer to red, yellow, and green pyramids.) Icetowers is an actual boxed game using Icehouse Pieces. It was sold for a while by Looney Labs but is currently discontinued. Rules for IceTowers were included in Icehouse: The Martian Chess Set, in a shared booklet with Ice Traders. It is also included in Pyramid Arcade. It was listed for 3-5 players earlier (e.g. in Playing With Pyramids) but now seems officially for 2-5 (e.g at http://www.looneylabs.com/rules/icetowers )