If you're not familiar with the concept, here's how it goes: you have ten "casts" (lives) to get to the exit of a level, but you don't have enough time to reach that exit, and you often require teamwork to complete puzzles and pass obstacles. Your help comes from your past selves: after time elapses on one life (or you choose to end it), another starts, and you go through the same level, with your past self as a ghost, doing the same thing you did before. If you hit a switch to open a door the first time, the other you will open it the second time so you can advance, and so on. In one case, I dropped down and hit a switch that created a bridge above me, allowing my second self to cross the upper platform.
In the second level, the game dropped a giant block on me right before the exit, requiring fifty button presses to defeat. The idea is that a combination of a few lives tapping at the same time will destroy the obstacle more quickly, allowing another you to access the door. The final level I played included enemies in the form of blocks that followed you, Boo-style, when you turned your back to them, and ended the life they touched. Of course, even that death has value to future lives, as your "ghost" will distract that enemy over and over again as you replay the level.
If there's an issue I had with the otherwise enthralling Echoshift, it's that the player characters are agonizingly slow in movement. Even the "jumping" (bouncing off bumps in the floor) follows an annoyingly slow arc, during which time the player is held captive, helplessly watching time elapse.