Wait, all of those tiles are placed randomly. But how do you then control the difficulty? Have you made some pathfinding system that determines how many tiles are needed with the generated layout?
If I'm honest, I never paid much attention to the timer or score. Instead I just tried to complete each round as quickly as possible, because I didn't know how realistic your estimates were for the available time. From the screenshots I now see that there is a bar at the top indicating the time. That is pretty usefull (better than just a number), but perhaps make it a different colour. Maybe also move the bar to the bottom and the other UI (text) to the top.