You are right. I solved this hold at work so I don't have access to this room on my home computer... but from memory:
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×I think I started out by piercing the seeps immediately to the west
How close can you get? I vaguely remember having to do some clever dancing with my sword just before the bomb went off. I'll try and remember to export my saves from my work computer in the future.
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×Your mission is to get that one seep in the lower left corner into the right place before the bomb goes off... don't waste time killing seeps if you don't need too (yet)
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×likewise for the remaining 3 "corner" seeps