green-button.css

green-button button {
    background: #02C385;
    display: block;
    width: 100%;
    height: 50px;
    color: white;
    margin: 8px;
    border: none;
    font-size: 13px;
    font-weight: 700;
    text-transform: uppercase;
    padding: 16px 20px;
    box-shadow: 0 8px 16px rgba(0,0,0,.1), 0 3px 6px rgba(0,0,0,.08);
    outline: 0;
    letter-spacing: .04em;
    transition: all .15s ease;
    cursor: pointer;
}

green-button.tsx

import { Component, Prop } from '@stencil/core';

@Component({
    tag: 'green-button',
    styleUrl: 'green-button.css'
})
export class GreenButton {

    @Prop() text: string;

    render() {
        return (
            <button>{this.text}</button>
        );
    }
}