The cheapest graphics card you can play it on is an NVIDIA GeForce 8200M G. But, according to the developers the recommended graphics card is an NVIDIA GeForce 6100. To play Gravity Ace you will need a minimum CPU equivalent to an Intel Core 2 Duo E8400. Gravity Ace system requirements state that you will need at least 4 GB of RAM.
Gravity Ace will run on PC system with and upwards. Additionally it has Mac and Linux versions.