Gain insights into practical CSS theming methods, delve into problem-solving, and discover the css-theming package to create highly customizable, dark mode-friendly apps in this course.

CSS isn’t what it used to be. Today, you’ll be hard-pressed to find a strong, straightforward, and expressive UI language that can beat modern CSS. As the tech world moves more and more towards web-based frameworks for UI, we start to see a bigger emphasis on highly customized looks for apps.

In this course, you'll learn how to properly develop apps that are theme aware. This course is split into two sections: in the first section, you will learn the practical methods and patterns around theming and discover common problems and their solutions. In the second section, you will get hands-on experience with the css-theming package and through it you'll learn how to customize every facet of your app. Most importantly, no matter the kind of app you're developing, users have come to expect dark mode support nowadays as a given.

By the end of this course you’ll be able to create stunning apps that are highly customizable by either applying what you learned in your own way or using the css-theming package.

CSS Theming for Professionals

# Introduction

A **theme brightness** defines the _mood_ of a theme. For now, we'll assume there are only two brightness levels:

- Light

![](/api/collection/6289435580694528/5438307556130816/page/6012244019118080/image/6653639637598208)

- Dark

![](/api/collection/6289435580694528/5438307556130816/page/6012244019118080/image/6549645963558912)

Having a dark theme is becoming more and more popular these days, so I'm sure you already expected a CSS theming course to talk about exactly that! But why do we have to talk about it? I mean, isn't a dark theme just like any other theme? Why should we treat it differently?

# Explanation

This comes around to human biology really, but this would be the wrong course for that! In short, there are certain things in the difference between a light and a dark theme that forces us to treat it especially, in particular when it comes to colors (which we'll talk about in the [next lesson](https://www.educative.io/courses/css-theming-for-professionals/mixing-colors)). Every brightness is associated with a certain basis for backgrounds/foregrounds in our app. A light theme always goes with lighter colors, a dark theme always goes with darker colors.

This lesson introduces the concept of a theme brightness.

Before Getting Started

Theory

Using css-theming

Samples

Theme Brightness

Introduction