Hope this helps with any level design questions you might have! (If it doesn't, ask below 
)
Main Blocks:
Low- Weakest type of blocks
Medium- Mid-level damage blocks
High- High level damage, two-three could stop a bird
Cubes- strongest, are also effected by portals and gels.
Special Blocks:
Large solid walls- take no damage and float.
70's desk- made up of 6 blocks, four squares in-between two thin blocks.
Gels:
Propulsion- Covered birds and blocks slow down slower.
Repulsion- Covered objects bounce on collisions with other objects, and non-cover able birds bounce on the puddle.
Fizzlers- destroy turrets that pass through them.
Companion Cubes- recommended to have one on every level.
Targets:
Birds/Lemons/Potatoes- nearly identical, extremely fragile, come in small and large sizes.
Bombs/Combustible Lemons- explode when destroyed, but not necessary to beat levels.
Tips:
Build from the ground up- it is much easier than to fight gravity...
Left/right move the screen
Entering "noone" (or any other word not used as an object id) will not spawn a object, this is usefulness for using birds abilities.
