I love this game with all my life. As a kid, when the DS console died down, I had two of them. One from my dad, that was red and black, and my sisters, who had a pink one with Shy Guy on it. I would mostly play on the red and black one and I ALWAYS played Nintendogs. Honestly, this is one of the best games that are related to pets from nintendo EVER. I've seen references made in games like Super smash bros ultimate.
I'm not sure if they still make them anymore, but if you're thinking about buying it, go for it! It really does keep you entertained when you're bored.
(By the way, if you have a 3ds, or a ds, you can insert the game card into a 3DS slot. It always works!)