This guide contains all the information I would've liked to know before starting playing.

1. Tametsi is a slightly more complex (and way better looking) Minesweeper.
2. If a cell contains a number, that number tells you how many mines are in the cell's neighborhood.
3. If a cell contains a ?, that means the cell's neighborhood could contain any amount of mines (even zero).
4. To examine a cell's neighborhood, hover your mouse cursor above the cell and press CTRL. It's way easier than having to remember what type of neighbor rule is in effect in that particular level.
5. To flag a mine, right click on the cell where you think the mine is.
6. To uncover a cell (when you're sure there's no mine there) left click on the cell.
7. You complete a puzzle when you flag all the mines and uncover all the empty cells.
8. The numbers in the upper right area of the screen are the amount of mines yet to be flagged. On multicolored maps, there's a counter for each color.
9. The numbers right next to lines / columns tell you how many mines are in that line or column. Hover above the numbers to highlight the cell, click to draw a line (it'll help you count).
10. All achievements can be completed by playing normally.
11. All levels can be completed without guessing, only by logic. But have fun anyway :)