How do computer difficulty settings work?

Hi,

I tend to play the computer on easy settings, as otherwise it will wipe the floor with me.

I understand how chess programs play their best game - they produce a move tree and evaluate the positions and choose the best one.

How do programs dumb it down? What algorithms do they use to choose less optimal moves?

THere is obvious answers like limiting ply search depth, maximum calculation time, but presumably there are more sophisticated techniques - so as to more accurately mimic weaker play. Perfect play to a certain shallow depth wouldn't give very realistic "weak play"..

I noticed how higher levels of computers they tend to not be so 'greedy' with peices and dont over use a peice say the queen. I have never seen a computer sac a peice to mate but I dont play at the highest level, but they do sometimes decline a queens gambit. (which is where white temp sacs a pawn)

On lower levels they tend to just see a peice they can capture which is unguarded and snatch it, and do not think more than 1 more ahead.

Stockfish does. I played a game recently where it sacked the queen for a two bishop checkmate the following turn. I was very impressed.