In terms of game file size, you will need at least 1 GB of free disk space available. Lightbender system requirements state that you will need at least 2 GB of RAM. Additionally, the game developers recommend somewhere around 4 GB of RAM in your system. The cheapest graphics card you can play it on is an NVIDIA GeForce 8500 GT. An Intel Core 2 Duo U7600 CPU is required at a minimum to run Lightbender.
Lightbender will run on PC system with Windows Vista and upwards. Additionally it has a Mac version.