It's a straight up one point per letter under your control. If you flip a letter away from your opponent, it's both +1 for you and -1 for them, a net swing of two points in the overall score.
Darker tiles aren't worth more - a darkened tile signifies a 'block' - if you control all the letters surrounding a letter, then that tile cannot be flipped until the ...
Word matches are based on matching first letters:
camp - invalid: all of this word is in an already played word, both match starting at the first letter
campers - acceptable: they differ at camps' "s"
scam - invalid: scams is longer both match at beginning
scampers - acceptable: camper starts with "c;" scampers is longer than scam & differs ...
A tile which you control can be defended (to use the official term) by controlling all 4 (or 3 or 2 along edges or corners respectively) tiles immediately adjacent to it. (Above, below, and to either side. Diagonals don't count).
A tile which has been defended can be used to complete words, but control of it will not change when it is used in this manner. ...