How do you complete level 42?

Level 42 is a hard level. You need to clear the shells down to get too the Fog areas and then use matches to cover the board with the fog. As with most level s making the boosters and wherever possible making combo boosters will be the most help.

The shells make the line boosters less useful so its probably best to use the alchemist character as your companion. And look to make bombs or beetles instead of lines. Luck will play a part so if you don't succeed keep trying as all levels can be passed with some luck.