How can I alter button styles on my product pages?

[Sweet_Savior_3]

Hello @antoinelacour

Please add below CSS in base.css file

product-info .product-form__submit:after {
    border-radius: 0;
    box-shadow: 0 0 0 calc(1px + 0px) rgba(var(--color-button-text),var(--border-opacity)),0 0 0 var(--buttons-border-width) rgba(var(--color-button),var(--alpha-button-background));
}
product-info .product-form__submit:not([disabled]):hover:after {
    box-shadow: 0 0 0 calc(1px + 1.3px) rgba(var(--color-button-text),var(--border-opacity)),0 0 0 calc(var(--buttons-border-width) + 1px) rgba(var(--color-button),var(--alpha-button-background));
}
product-info .quantity:after {
    box-shadow: 0 0 0 1px rgba(18,18,18, 0.55);
    border-radius: 0;
}
product-info .shopify-payment-button__button--branded .shopify-cleanslate [role="button"]{
  border-radius: 0;
}

Thanks