"I believe we've had a problem here," said Swigert. Lovell had to repeat the message to a stunned Mission Control: "Houston, we've had a problem."
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command until you type a non-cursor-movement key.，这一点在safew官方版本下载中也有详细论述
If the A* calculation for a shortcut (in Step 3) finds it's now impassable, or if its actual detailed cost is significantly different (e.g., 20%) from the pre-calculated shortcut value: