Hello,
I want to share some great levels with you!

Desert Disaster (1 player) by 
http://ie.lbp.me/img/ft/ace4869590362aa189d61cd7fb8b8c86b039b5a5.jpg
(Picture wasn't made by me)

This level is really cool. I love the theme and how the creator designed the platforms. It's also challenging. If you want to play a cool and challenging platformer, play it!
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Thunder mesa cup by BzR242

http://i6.lbp.me/img/ft/f46d1291e2237294863ababf4fc9c7d60deeea72.jpg
(Picture made by me)

This level is also great. A similiar theme and a cool design of the road. It's a racing game that can be really challenging. I recommend playing it!
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Dschungelruinen by Baekos2507
http://ib.lbp.me/img/ft/04bb6e9486db1625d66b899a50e531bb41955492.jpg
(Picture wasn't made by me)

This level was Baekos' last level in LBP. I personally think, that this level was a good one too. It had cool music. I also want to mention the gameplay elements. Many different elements come together. You need to catch a swimming woodpiece, change to the other woodpiece and avoid the spikes aand so on. There are also some secrets to collect. They award you with extra points. All in all a good platformer!
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Aquatic Cavern by ola2020
http://i3.lbp.me/img/ft/7934f86b33fc76d6d6b8d4b23f754eab9b04bb98.jpg
(Picture made by me)

This level has a great mood. Relaxing music, smooth gameplay and cool light effects. I like this level. Great work!
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That's pretty much it for today. I think I'll post more levels in this thread in the future. Keep in mind, that some of the levels got posted by the creators here on LBF so don't get confused.

In conclusion I have to say: It's not a waste of time to play all those neat levels.