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Level 15 - INILFTG
The answer to this puzzle is:
Words: FLITING, TILING, GLINT, GILT, LING, TING, FLIT, INTI, NIT, FIN, TIL, FIG, GIT, GIN, NIL, LIN
Bonus words:
FLITING, TILING, GLINT, GILT, LING, TING, FLIT, INTI, NIT, FIN, TIL, FIG, GIT, GIN, NIL, LIN