Radio buttons horizontal instead of vertical

Hello,

It's possible, first you have to define your characteristics display in your Main HikaShop configuration, then in Product options tab, you have the Characteristics selection method :

Then, you can add custom css command in order to change your radio button design, you may find on internet lots of different way in order to have better design, and I'm quite sure you will find already existing vertical design code.

In order to add your custom css in your frontend css file, you can have a look on this tutorial

Regards