Definition
To return to the starting point of a plan or task, typically because a previous effort has failed.
指计划或尝试完全失败，必须从头重新开始。
If this approach doesn't work, we'll be back to square one.
如果这个方法行不通，我们就得重新开始。
The project was back to square one after the funding was withdrawn.
资金被撤回后，这个项目又回到了起点。
After months of development, they found themselves back to square one, needing to adopt a new framework.
经过数月的开发，他们发现自己又回到了起点，需要采用新的框架。