"Good luck" not really intended to be difficult. It's just bigger, for people who want little bit more classical experience and give a test to game mechanic.
| Difficulty | height | width | length | mines per layer | shafts per layer |
|---|---|---|---|---|---|
| Easy | 3 | 5 | 5 | 2 | 4 |
| Hard | 5 | 5 | 5 | 4 | 2 |
| Good luck | 6 | 7 | 7 | 10 | 6 |
Yeah, layers mechanic with arrows need more polishing.