Chill your rocks glass as you make your drink.
Muddle the pineapple. Set some aside if you want to garnish with it. Pineapple is full of fiber, so muddling might be a bit challenging.
If you LOVE mint, and want the entire world (and beyond) to be minty, muddle your pineapple with some mint.
In your rocks glass, toss the chilling ice and add fresh ice.
Add your gin to your rocks glass.
Strain your muddle pineapple (and maybe mint) into your glass.
Top with a little, or a lot, of pineapple juice to taste. This will depend on how much fruit you muddle and how much you love pineapple.
Finish with some seltzer for added flair.