Once you hit the play button for Parkour Block 3, you'll be taken to the start screen. Here, you can change the settings, select a level, or just Start. The background of the start screen shows walls with blocks on them, with a lava scene on the floor.
It all looks quite a bit like a Minecraft area. Once you select to start, you begin in a room with blocks to jump on. You can either use the arrow keys or the WASD keys to navigate around the room. The space bar allows you to jump. The goal is to jump onto the various blocks without falling off into the lava underneath you. If you do fall, you will hear a pained sound, and then you will start over at the beginning of the level. You will also hear step sounds as you move. The controls for turning around appear to be difficult, but the control for moving left, right, forward, and backward correspond to the normal control as you would expect. You have to time the jumping correctly with moving forward in order to get to each block, otherwise, you will fall in the lava over and over again.
The game allows you to adjust the sensitivity in the Settings screen so that you pushing a key like the one for moving forward will either move you a small amount or a large amount depending on where you have that level set. It may take some adjustment to get it right.