Making levels could be hard or easy. Since your game looks simple, you can try make levels which are:
1. Bigger than previous levels.
2. More complex than previous levels.
3. Has more obstacles/hazards/enemies than previous levels.
4. Literally has more turns and branches than previous levels.
5. Combination of the above.
The results may not be liked but just make as many as you can then play them all. After that assess them and pick the best ones for your game.