Duplo number building challenge

I've been trying to find different ways to encourage my eldest son to play with the toys he already has as he's getting bored and frustrated by being at home all the time.  I've had a few failed ideas which he's refused to even try, but one which he was enthusiastic about once he realised what it involved was a Duplo building challenge to make large numbers.

Duplo numbers and blocks needed to make them

I made large numbers 0, 1, 2 and 3 from Duplo blocks, and made a pile of exactly the same set of blocks for him to use.  The challenge was for him to make exactly the same numbers with the same colours and arrangements of blocks.  As I've bought almost all of our Duplo second hand, we don't have many instructions and tend to build whatever we fancy, so he's not used to building something to a set design. He wanted to start out by modifying my numbers, but I encouraged him to give it a go making the same as the ones in front of him, and once he decided that they wanted identical twins and he could make crane sound effects as he built, he was keen and set to work.

It was interesting to watch (and listen to!) his logic.  He decided to make number 1 first as it was easiest, and he had no trouble replicating my pattern of blocks.  Then he decided to make 0 and he started at the bottom and built upwards.  He got in a bit of a muddle about which colours went on which side and took it all apart rather than just going backwards until the incorrect blocks had been removed.  Undeterred, he started again and got it right.

Part way through building
Number 2 and 3 were more of a structural challenge as he couldn't just press down on the existing blocks, he had to be careful about how he put them on and - for the tops - not just build upwards in order.  I feared he'd give up when number 2 fell apart when he pressed on the top where it was unsupported, but he had another go and asked me to hold part of it.  For number 3 he made it easier for himself by building it right next to the 3 I'd made so it was really simple to see which colour block he needed next.

Proud of his completed numbers

Once finished, he launched into a round of asking me what pairs of numbers made when added together.  He has grasped the idea that zero means nothing, but he often asks questions about what things make when added to zero, or what zero plus zero makes.  We spent a while discussing sums - some of which he answered himself - including some with much larger numbers that he chose e.g. 80 + 80.  I'm not sure whether it was the numbers which made the Duplo building interesting, but I'm going to try another building challenge for him soon as we have lots of Duplo and lots of time to fill!