This is the first world you play. The main hub between levels is the Boy's treehouse. You will have 2 maps on ground floor inside said treehouse.
The larger map is the one you will need to choose your level. Of which there are 10. It starts off nice and simple, and some easy puzzles to complete if you are also going for all 30 chests within this world. Really not hard to find.
To complete each level, you just need to find the Glowing/sparkling jellybean at the end of the level. Not hard at all, and breaks you in gently.
Anyway, the last level will be completed not after picking up the Glowing orange jelly bean at the end, but after the boss fight. No need to fear, its really very easy.
Boss: Giant black worm.
Stage One: Give Blob the yellow jelly bean, and transform him into the anvil. Push him towards the worm, an he will attack but hit his head and lower the poles either side of the screen.
Stage Two: There will be a horizontal pole above you with an electrified section in the middle. Give Blob an orange jellybean to transform him into a trampoline, and jump up onto the slightly thicker piece of the pole. The worm will attack and shock himself.
Stage Three: The final stage here. Get ready to give Blob a red jellybean. But wait until our worm friend launches skywards. You will see an elliptical shadow on the floor. When it stays still, press an hold B to throw the jellybean over to the shadow, and the worm will drop through into the water.
A short death animation will follow, and an easy 25g will be yours for keeps.
If there is anything you wish me to add or change to the guide, let me know and I'll adjust it for you. If it helps, give it a thumbs up so I know it's all good.