わからない個所を教えてください。
The idea is amazing. In another couple of seconds, I see that I can do the same from my front gate, turning right instead of left. It has never occurred to me before that this might be possible. You get to the rocks and the lizards by going up the tree and over, that is how it has always worked. I have never imagined— （前回の終わりの部分です）
‘What is it?’ he says.
‘Nothing.’
‘You looked weird.’
‘I was just thinking,’ I say.
‘Oh.’ He is quiet for a moment. ‘How old are you?’
‘Six.’
‘I’m seven,’ he says. ‘So. Where are these lizards?’
I look around me. ‘They’re not here any more,’ I say. ‘They go away when it’s evening.’ ‘Oh,’ he says, sounding disappointed. ‘But you said they were here.’
‘They’ll be here tomorrow,’ I say. ‘If you could come tomorrow, I could show you some.’ ‘Yeah? OK.’
At that, we both hear a woman’s voice calling, ‘Jamie!’ ‘That’s my mum,’ he says. ‘I’ve got to go. I’ll see you tomorrow. Bye, Alex.’
‘Bye,’ I call after him, as he runs off around the end of the wall. He runs quickly and easily, his feet sure on the uneven ground, almost as if he is floating. I trudge back to my end of the wall, but rather than climb over, I go around the end, and find to my astonishment that what I have worked out is right: after getting through the fence, I am outside my own front gate. The discovery makes me smile as I go inside, and the smile is made wider by the thought that tomorrow, Jamie and I are going to look for lizards together.
******************************************
主人公のAlexはartistで、展示会に備えるために、幼い頃過ごしたイタリアに戻ってきています。（この英文は子供時代の回想シーンだと思われます）
He runs quickly and easily, his feet sure on the uneven ground, almost as if he is floating.のhis feet sure on the uneven groundは、彼の足はでこぼこの地面の上で確かに、という意味ですか？sureは副詞ですか？
教えてください。 お願いします。
