WITHIN system requirements state that you will need at least 4 GB of RAM. An Intel Core i5-4590 CPU is required at a minimum to run WITHIN. In terms of game file size, you will need at least 125 MB of free disk space available. The cheapest graphics card you can play it on is an NVIDIA GeForce GTX 970.
WITHIN will run on PC system with Windows 7 SP1 or newer and upwards.