TCL and LG have been teasing the idea of an extendable display on smartphones for some time, and now, we finally get to see a working prototype courtesy of a third brand. Today’s Inno Day 2020 event unveiled the Oppo X 2021 concept smartphone, which is all about its “continuously variable OLED display.” With a simple swipe on a button, the phone is able to transform between a regular 6.7-inch size and a tablet-like 7.4-inch size, and the software interface adapts accordingly for optimal experience — be it for single-hand usage or for multi-tasking.