Obstacles

The puzzles get difficult over time. As soon as you progress, being efficient with your chains, and proper usage of the tools will not be enough. The game will throw lots of hurdles right in the puzzle board.

Rats

Rats will start appearing on the fields. Every three turn they will move into the nearest fruit, or vegetable, and if there are none of both, they proceed to the nearest grain. There are certain grasses that attracts rats, though.

Gases, Rubbles, Lava

The mines have the most annoying and most plentiful obstacles. Gas tiles appear when you start chaining long tiles of dirt. You can pop them out immediately, but that means one wasted move. Moves are precious in mines because unlike the fields, you can't "preserve" the tiles for the next visit, you can only extend by consuming iron ration or using runes.

When three or more gas tiles come in contact they react after a turn and explode. Every tile around the area becomes rubble. You can't remove rubble unless you chain them in a considerable length. Lava is like the burning tile in Bookworm. Basically, when ignored, they burn through the board destroying each and every tile below it until it reaches the bottom and then explodes.

Islands

Islands appear on the sea puzzle board. They don't do anything other than block the boat's or disconnects shallow or deep water tiles from connecting.