From the official website (http://www.tension-game.com/about_en.php):
"Tension – a survival adventure game, in which you have to stay alive in the hostile world of Void and to get out from it as quick as possible. The choice is either to support life in its horrifying Hunters or its mournful girls or strip them of it. The way you pass through The Void is the way it changes. The way it reflects upon you.
The surrealistic world of Tension is based on a single resource that grants the ability to live and act – Lympha. Each color of Lympha possesses its own character and unique properties – both useful and dangerous. Only Lympha gives life, but it can take it back as well. Hunters’ blood, captured creature, gracious girls, tree brought to life, just everything is the source of Lympha. Any action you take: battling an enemy, talking to a Sister, hunting, searching, traveling – the price in exchange is Lympha.
The dynamic, interactive environment and the severe resource shortage constantly put the player into unexpected circumstances. Although the player is free to use any colors any time he should mind his global strategy, since the finale will turn out the way the world is painted. The gameplay in Tension is non-linear the ending (one of the 11) depends on the color and the amount of Lympha used."