'delightful at' is not a correct or commonly used phrase in written English.
It would be more grammatically correct to say 'delightful in' or 'delightful by/at.' Example: The garden was delightful in the springtime, with its colorful flowers and fragrant smells.
A passionately systematic scientist, Maudslay spent years in the field, and there's a delightful "at home" self-portrait of him sitting at a desk in the study he had rigged up in the ruins at Chichén Itzá.
It was delightful at times, to be sure.
A kind-hearted soul, who had adopted a boy with cerebral palsy, who bought ice-cream for his congressional pages and was delightful at dinner, both to Democrats and Republicans.
Belt-Up's Macbeth is unlikely to be delightful at all, but it should be suitably atmospheric and sinister played out in the House of Detention in Clerkenwell from tonight.
Eight years, two discredited presidents and an endless smear of negative publicity in the making, Rio 2016 finally juddered into life with an opening ceremony that was at times delightful, at others a little rickety and home-made.
A week later Haydon paid it a visit, and his diary gives us the first record of the benefits of free admission: "It was delightful at last to walk in to the Gallery just as you felt inclined without trouble or inconvenience.
Students at Oregon State University dressed up their bipedal robot, Cassie, in a delightful AT-ST costume.
The chef made one particularly delightful dish at Poodam's that also appears at Zabb Elee: hor mok ($11).
A delightful view at Audubon Zoo is of human kids at the Cool Zoo water park.
Calakmul is a delightful place, at least for now.
Smashbox Photo Finish lipstick in Delightful, $22 at Sephora stores.
