[Challenge] Can you solve this fun puzzle?

Instructions: play vs engine 3200... till you get it. There is one main forced solution, and at least another if the black/engine doesn't play the best defense.

Another one. WHITES MOVES and mates (in x moves):

The first #6 is simple even without engine, just capture 6 times on f4. Suppose that wasn't the intention.

The second one I haven't found yet.

Thanks for the feedback! First one is correct, good job! White can also (almost) mate from the upper-left, but if black plays perfectly then it's fine (3200 engine wont find the correct moves tho).

For the 2nd one: keep trying, by playing vs the engine (3200 or highest u can set), till you get the win/mate.

What engine lets you set up illegal positions? I wish stockfish would allow this so bad..

I don't think StockFish or Komodo objects to setting it up (on chess.com). Both will also solve the first puzzle (haven't found the second solution yet) after you give them a few moves which shows its limitation is not about legality but about capacity. SF does not generally check legality except the severest cases like "a missing king".

Btw, there is a bug in setting up chess positions in general in chess.com's analysis interface which causes it to freeze at random times. Therefore, always select Komodo as your default puzzle engine before you set up a position. Once the position is loaded you can switch to StockFish. Note that your default puzzle engine is always active while you enter a diagram as you can see in the scoring bar on the left. For some weird reason that process may interfere with the interactive editing of positions. Not sure that happens on all systems but most certainly on mine!

Any apps that allow illegal position set-up?

I am absolutely sure all apps and applications allow the setup of illegal positions since there are no classes of illegal positions. There are the "obvious illegal types" with 1 king, 9 pawns, 52 units, 10 white queens, (wBh1, wPg2), and the less obvious types where you need to retract 39 moves into the past before you discover it's illegal. There are tons of the latter as well but they are all classified as just "illegal positions". That's where for instance Blathy went wrong. He made a distinction between "acceptably weird" and "unacceptably weird" but the only valid definition today is "a position that one could not arise from a legal orthodox chess game".

Btw, Illegal orthodox positions are OK in fairy chess where retrograde analysis does not apply (unless the author wants it). So this puzzle counts as a fairy - as anyone will assume upon a brief inspection

Even in terms of piece count, I can't find any app that allows such setup. Stockfish says "too many pieces" even if there is only 9 pawns. Ironically it does allow set upside like a bishop in the corner behind the pawn or triple checks.

I didn't say they allow all illegal positions. It's just a random selection based on arbitrary criteria in the designer/programmer's mind.

And I don't think it's StockFish, it's the Puzzle_GUI which is a different entity. The current chess.com versions of SF and Komodo definitely solve positions like this one though I simplified it somewhat by giving them the first 4 moves. I know that older versions crashed or yielded weird codes like +153 but they are improving.

Note that these positions can be entered with FEN strings which circumvents the stepwise addition of pawns and other procedures which test the tolerance of the Puzzle_GUI.