The document interface is used as the entry point to the DOM.
.querySelector() - returns the element that matches the selector. Must be a valid CSS selector string.
.currentTime - This property sets or returns the current position (in seconds) of the audio playback.
.play() - starts playing the current audio or video.
.classList - returns a list of the classes on a given element. Many helper methods such as .add() or .remove() can be used to manipulate an element's class values.
.propertyName is a DOM string containing the value of a CSS transition property.
.addEventListener() - a function that will be called whenever the specific event occurs. Can be used to listen for all types of events.