Thanks for trying the demo and taking your time to write this feedback! I think I'll be able to address all your points in at least some way in the next update.

Some thoughts on your points:

1. I think increasing the pickup range would solve this. There's also an inventory limit of 50 items, I think that's why you weren't able to pick up anything after some time. I should probably show this limit somewhere

2. Seeds can be found by smashing the cubes that have squares on their faces. Plants can only be placed on sand right now.

3. Ladders should help with that, although currently there's no point in going higher than 30 blocks over water unless you want to build a very vertical garden. I plan to add blocks that spawn only on the higher levels to motivate player to use all the available space, but I agree that the level generation algorithm should be improved before that.

4. It works correctly on my computer so this may need some more investigation. Were you running the linux or windows version? Do you have a generic mouse or something fancy?