Esperanto prepositions "en" vs "al"
I've been doing Esperanto for several months now (I've reached level 9, which is good), but I still get confused about the two prepositions. Would anyone know the difference between them?
For exemple, I've seen both of these sentences: Ni iras al la parko. Ni iras en la parko.
Ni iras al la parko. = We are going to the park.
Ni iras en la parko. = We are going in the park. (Note that this means you are already inside the park, walking around.)
Ni iras en la parkoN. = We are going into the park.
I've been thinking about that, but in my notes I had the same translations for both sentences. However it's quite possible it was my mistake. Regarding the third option (the "n" meaning a direction) - Why doesn't that work on the first one as well? It's also a direction.
Some prepositions already indicate direction, so they don't need the -n ending.
This was the clearest list Google brought up for me on short notice:
-n can show direction or destination of movement: In limited cases, -n can be used after a preposition to show an action that is moving in a direction, as opposed to action occurring in a place. Not every preposition in Esperanto can be used with -n to indicate direction of movement. The prepositions that can be used with -n are: sur, sub, en, apud, antaŭ, malantaŭ, post, inter, trans, ekster, super, ĉirkaŭ, and kontraŭ.
Mi promenas en la arbaro. – I walk in the forest.
Mi promenas en la arbaron. – I walk into the forest.
Mia amiko kuras trans la strato. – My friend is running, on the other side of the street.
Mia amiko iras trans la straton. – My friend runs across the street. (my friend was on this side of the street, but is now crossing to the other side)
Li saltas sur la tablo. – He jumps on the table.
Li saltas sur la tablon. – He jumps onto the table.
-n can also be used to show direction after adverbs that indicate location:
Mi estas hejme. – I’m home.
Mi iras hejmen. – I go home. (hejmen = homewards, toward home)
Vi estas tie. – You’re there.
Vi kuras tien. – You are running over there. (to that place, toward that place)
(from this pdf, page 8: http://www.ikso.net/libera/pdf/chap8_en.pdf )