The only current way known to finish the game is to have collected all eight gems. Once you've done this, go back to the main hub and open the drawer on the bottom of the bookcase. Inside you will find a ring. Click on it, and it'll bring it closer to you so you can place each of the collected gems in their slots. The order is meant to be the color of the rainbow, being the following;

Red, Orange, Yellow, Green, Light blue, Dark blue, Purple, Pink

Once you have placed all gems in the correct order, a symbol will appear on the bottom of the pillow the ring is resting on. Remember this symbol. A cutscene will (or is supposed to) play and then you will be confronted by the game's antagonist Pantagor, who splits a tree stump into three copies. Click on the tree stump that has the symbol you saw earlier, and the final cutscene of the game will (or is supposed to) begin playing.

Once you see the certification screen, as per the speedrun's rules, the game has officially finished.