In order for you to play Shelter on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
OS X version Leopard 10.5.8, Snow Leopard 10.6.3, or later.
Processor (CPU):
2.6 GHz single core
Memory (RAM):
1 GB RAM
Graphics Card:
OpenGL 2.0 compatible video card with 1 GB shared or dedicated RAM (ATI or NVIDIA)
Storage:
2 GB available space