Childcare expert LeShan / SUN 9-20-20 / Jazz composer Beiderbecke / Yellow variety of quartz / 14th-century king of Aragon / Unpopular legislation of 1773 / Internet meme with grammatically incorrect captions / Philosopher who tutored Nero / Tokyo before it was Tokyo / Game in which each player starts with score of 501 / Norse troublemaker

Constructor: Sam Trabucco

Relative difficulty: Medium-Challenging (mid-11s)

THEME: "Word Ladders" — the words in the word ladder (succession of four-letter answers where one letter is changed with each iteration) are actually "ladders," in the sense that they act as paths along which a couple of Across answers drop or rise three levels respectively:

Theme answers:

• SURPRISE PARTY / UNDESIRABLE
• STERILE GLOVE / TRAVEL IRON
• PROFILE PIC / FOR THE LIFE OF ME
• FRUIT FILLING / MOLLIFYING
• ROOT OF ALL EVIL / VANILLA FLAN

Word of the Day: LESTOIL (99A: Clorox cleanser) —

Lestoil is a registered trade name of Clorox for a heavy-duty multipurpose cleanser product, used to remove extremely difficult laundry stains, dissolve water-based and oil-based paints, and clean grease, oil, paint, and adhesives from floors and surfaces.

It was introduced as a dry cleaning fluid for laundry in 1933. (wikipedia)

Not sure how to describe my feelings here. As an architectural feat, it's pretty impressive. Takes the (awful, shopworn) theme concept of the word ladder (which here goes from RISE to FALL) and soups it up by making the rungs of the "ladder" into actual ladders by which themers "rise" and "fall" (three rows in either direction). Conceptually it is tight and interesting. And yet I found solving it tedious. Once I got the gist of the theme, I just had to remember that there was going to be rising and falling, so nothing interesting really happened except the fussiness of keeping the rising and falling straight, and then, further, there was so much jarring fill that it just ate into any of the whimsical pleasure the theme might have provided. LESTOIL ... ??? ... never heard of it. Never seen it. Hasn't appeared in the NYTXW since I started blogging (fourteen years ago this week!). CITRINE? (71A: Yellow variety of quartz) I'm sure it is what the puzzle says it is, but again, I got the answer and just had no way of knowing if what I had was right (though CITRINE at least sounded plausible—LESTOIL looked wrong as hell). And what year is "I Love It" even from? You could've at least included that in the clue, because ICONA (!?!?!?!), yeeow, no (36D: "I Love It" duo ___ Pop). One hit, eight years ago. I mean, even if ICONA Pop were somehow ABBA-famous, ICONA on its own is never, ever, ever gonna be good fill. There's also lots of crosswordesey stuff that made me make faces (PETERIV ATEIN USRDA ADREP EDO ETTU NEE EES (ugh) CINES EDA NOE LGS AOL ESAU ELL ESO ETC. etc.). So I acknowledge the architectural feat, but as frequently happens with architectural feats, the payoff at the level of solving pleasure just wasn't there. Maybe if the fill had been stronger, the thematic workmanship could've carried the day, I don't know.