Undergraduate / "big cardboard box" - UPenn, JHU, Brown, Rice- Common App [4]

Being the procrastinator that I am, I waited until the last mintute to whip up an essay for the Common App...
I'd really appreciate it if you could take a brief glance at my essay, looking for any spelling/ grammatical errors in particular.
Please critique to your heart's desire! I will be more than willing to read your essay in return!
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Many children grow up playing with their favorite dolls, action figures, or Lego sets. I never bought into any of this hype as a kid, however. You see, I had a big cardboard box. Now, this was not just any old cardboard box- this was a house, a skillfully crafted two-story abode complete with windows, a locking door, and customized wallpaper. Within these four cardboard walls I was a leader, a maestro, or a renowned physician, depending on the day. Robert Louis Stevenson beautifully captures the relationship between me and my fictitious fortress in the third stanza of his poem, "My Kingdom:"

And all about was mine, I said
The little sparrows overhead,
The little minnows too.
This was the world and I was king;
For me the bees came by to sing,
For me the swallows flew.

This cardboard contraption was a realm that I could call my own, and I was its sole ruler. As I look back over the years, I realize that this place of imagination and playtime provided me with the reagents that catalyzed my early self-discovery.

Some days it was a hospital. The health and well-being of my entourage of thirty-something stuffed animals relied on the abilities of both me and my trusty 7-piece doctor's kit. One of my favorite rituals would be to watch the emergency room veterinarians on the Animal Planet channel and then race back into my own infirmary to mimic their procedures. At other times the house served as a school, and I would lead my animal friends through the properties of static electricity, snails, and subtraction. On Monday, I could be the Itzhak Perlman of rubber band guitar preforming in Carnegie Hall, and by Thursday, a weathered paleontologist uncovering the fossilized remains of an ancient beast. I was a pathfinder, capable of venturing from one end of the planet to the other from the comfort of a pink plastic chair.

I eventually outgrew my house, but the adventures I embarked on inside its closed doors are still embodied within me. The furry figments of my imagination have morphed into boisterous basketball-wielding adolescents I've coached, and giggling cerebral palsy patients I have taught English to. My adventures overseas have come to life, from mastering the public transit system in Shanghai to haggling with vendors in their native language at an outdoor mercado in Mexico. As I have grown, so have my interests and passions. Although my plastic doctor's kit is long gone, I still fuel my love for medicine by working alongside doctors at a local free clinic. I have discovered new ways to channel my desire to learn more about the world around me, whether they be in the form of donning a white lab coat or hurtling through a wooded aviary in pursuit of a rare bird.

Eight months from now, I will once again outgrow a place that I have called home and find myself situated in an entirely different environment: college. I would like to think of college as a new setting that will nurture and broaden my curiosities; a setting where I will not simply regurgitate information, but explore and experiment with whatever is presented before me. Regardless of where my future pursuits take me, though, I will never forget all that I learned while under a cardboard roof.

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My conclusion is not complete yet. Any suggestions?

Thanks in advance!