I am at the dining table, colouring in a fiendishly complicated line drawing. The theatre scene comprises intricate parts: rows of tiny seats; an abstract set design reminiscent of trees.
As I shade the fish-scale-sized seats with red and blue colour pencils, my almost-six-year-old son leans over to look. "Very nice," he says, encouragingly. "Keep going."
At the ripe age of 38, I have rediscovered that most kindergarten of pleasures: colouring. Apparently, so, too, have others. Adult colouring books now reign at the top of international bestseller charts, while the genre has become a publishing phenomenon.
Scottish illustrator Johanna Basford's Secret Garden and Enchanted Forest colouring books combined have sold more than two million copies worldwide. Her third, highly anticipated book, Lost Ocean, will launch on Oct 22.
Meanwhile, Welsh artist Millie Marotta's Animal Kingdom colouring book is No. 1 on the Amazon.co.uk bestseller books list - ahead of Harper Lee's Go Set A Watchman.
Colouring is a manifestation of seeing. Who needs to see eye to eye, when you can obliquely experience someone else's eyeballs and try to understand their strange spectrum?
So popular are such books that major publisher Penguin Random House have begun promoting these once-indie titles. Besides Basford's Lost Ocean, Penguin Singapore has on its list of upcoming releases The Magical City by British designer Lizzie Mary Cullen, Escape To Wonderland by British artists Becky Bolton and Louise Chappell, and Elsewhere by Japanese artist- film-maker Joji Koyama. Prices range from $17.50 to $27.
For a while now, colouring has been an ironic hipster thing. Colour Me Good titles, bearing the colour- able mugs of heart-throbs such as Ryan Gosling and Benedict Cumberbatch, make good gag gifts for your urban-farming, artisanal coffee-drinking pal. Off-beat creations such as Unicorns Are Jerks (2012) by Theo Nicole Lorenz, which shows the mythical creatures farting in elevators and eating all your fries, are good for a laugh, even if you leaf through them without lifting a colour pencil.
But, somehow, adult colouring books have managed to become mainstream - becoming what The New Yorker called last month "a massive new industry category".
What is the allure of this pastime for grown-ups?
Publishing director Philippa Wingate of indie publishing house Michael O'Mara, which has published Creative Colouring For Grown-Ups and Art Therapy: An Anti-Stress Colouring Book, says the books appeal across the board because stress is an increasing part of modern life.
"We certainly think nostalgia plays a part in the popularity - taking people back to a time when they coloured as children," says Ms Wingate. "In adult life, we suspect people value the rare opportunity to feel that they are being artistic and creative."
Besides the anti-stress and physical therapy properties of colouring, she adds, such books are taking off in a big way as a communal activity: "People like to colour in groups, enjoying wine and conversation while they create - it's every bit as sociable as going to a book club, but without the homework."
A preschool teacher friend of mine is hooked on Basford's books because it is more convenient and less stressful than her previous hobby of scrapbooking.
There is a treasure hunt element to the exquisitely detailed designs as well, with little half-hidden motifs to spot. "When I'm colouring, I get lost in my own world, even sitting at Starbucks," she says. "It's therapeutic and lets me zone out while doing something fun and somewhat creative."
Another friend, an interior designer, says her young kids understand that they are not allowed to colour in mummy's special colouring books, which she enjoys filling in with special fine-tipped markers. When I texted her to complain that my set of 24 Faber-Castell watercolour pencils was woefully inadequate for adult colouring purposes, she texted back: "Yeah, very pathetic, right?" (I went out and bought a 48-colour set.)
While the trend has been hailed by The Huffington Post as the 21st-century alternative to meditation, others are worried by it, claiming arrested development. By choosing to mindlessly colour within the lines, argues some observers, adult colouring fans are merely in denial, retreating into childhood and refusing to grow up.
The truth is a lot more complicated than that, I suspect.
As a child, I had refused to colour in my colouring books, afraid to sully their blank precision with my imperfect colouring.
To my three-year-old mind, the printed picture, even if it was only of Hello Kitty, was permanent and immutable. Perhaps, aware that my life and selfhood was beginning, I refused to commit myself on paper to a certain palette. Shifting homes as a teenager, I left behind a lot of pristine colouring books.
It is only as an adult that I have found the courage and confidence to add colour to these scenes. Part of it is because the preciousness my penniless kid self associated with these finite colouring books has evaporated.
But another reason is that colouring is a manifestation of seeing. No two people view colour the same way, as the white-gold/blue-black dress Internet controversy has shown recently.
The way we mix and match shades, thus, is highly individualistic. We colour at the start of our lives to practise how to see the same way that others do; to close ranks and align against ambiguity - that is, we are schooled that lions are yellowish-orange; grass is green and skies are blue; and that covering everything in a thick layer of black crayon will get you sent to the child psychologist in double-quick time.
But we begin, in mid-life, to embrace colouring differently and freely. And, with people uploading their colouring results onto Facebook and Pinterest galleries, we further appreciate this difference and the variety it brings to life. Who needs to see eye to eye, when you can obliquely experience someone else's eyeballs and try to understand their strange spectrum?
The best colouring designs encourage that too. When I work on the sample pages of Magical City and Elsewhere - swirling seascapes with cliffs that look like dragon's teeth and clouds like fire breaths; trees with trunks that, Escher-like, seem to shade into one another - my mind is challenged to interpret this imaginary topography.
Where to apply darker shades to denote lower-lying areas and where to use a bright hue to make that surface 'pop'? Each colour-rendered scene is an interpretation, a collaboration with the artist. It is incomplete and unstable without me.
It is true, colouring is comforting because it offers respite from my real, messy life. There are clear lines to guide me, to make sure that the finished product is beautiful - lines not available in careers and parenthood.
But there is individual chaos too, in this order. The predictable nature of what you will get goes hand in hand with its unknowability until you are done.
That duality is what makes adult colouring so satisfying: comprehending the tension between stasis and change is key to growing up gracefully. You get a certain set of parameters in life, you add to it very nicely, and then you keep going.