Fitting everything in the box room (shocking drawing included!)

[mynamechangemyrules]

My son has the box room. There's no alternative to it being used by him.
At the moment he has a 'loft bed' with a desk running under it. He then has a chest of drawers and a little bookshelf to the right. He's a keen gamer and almost 12 so does homework each evening too.
His room is an absolute tip all the time and he just gathers crap on the desk when all he really uses on it is the laptop and a little writing space. It runs the whole length so it's a lot of space for shit. He's also moaning as he gets bigger about climbing up and onto the bed which is v high and close to the ceiling. I absolutely hate his room and it's a pit! Every time I moan about the mess he moans about the size of the room and we go in circles.
For his birthday in a few months I wondered about getting a low bed with drawers all under it and fitting a desk in somewhere. But I don't have a creative or logical mind (I barely have a mind at the moment tbh!) and I cannot work it out. The budget as always with me is basically zero but I'll keep an eye on marketplace etc once I work out what I need... any ideas?!
Should I put the desk where the drawers were? Or try to get it running under the window?
Apologies for literally the worst picture ever!

Ok I've also realised the black background on my phone doesn't help 🤪

Same sizes as my smallest. We did everything from IKEA.

Built the bed out if those 4x1 and 2x1 cube units, with a box in each cubby. This went along the long wall plus a small desk which overhung the bed slightly.

4x1 cube units as a bedside table plus more storage boxes. 2x1 might have been better but we misbought.

On opposite wall a 100cm IKEA low depth (I think 35cm) wardrobe and the same in a 50cm wide without a door to use as shelving.

It was a huge amount of storage space and easy to get in and out of so long as the floor was kept clean.

Thank you! Love a bit of Kallax and already have them in the back room so they could be repurposed. Was the whole bed made from them..?! Or built around a bed frame?

Two kallax 4x1s I think can be hacked into a bedframe. You need to make sure ventilation is ok.

We have a vaguely similar size and we found a standard length bed in a small double size, and swung it across the width, under the window. The extra length of a European bed would have been a problem whereas the extra width we could afford, and it made it feel luxurious. DS now had a square floorspace rather than 2 little strips and the room feels twice the size. We put a built in 75cm IKEA pax wardrobe in the bottom left corner of your black pic. It has drawers in the bottom, hanging space above and contains all his clothes. He has a low metal bedframe which was the smallest end to end that we could find. He actually doesn't have a desk because he never used it, but a small foldaway desk like they use for exams might work for your son. I found a tiny 2 cube unit on Amazon and that does for a very trim bedside table with a bit of storage.

My plan was to buy solid, wooden drawers on wheels for under the bed, but I haven't yet because we have nothing to put in them.

Just to add consider an ottoman bed. We didn't because they looked like a PITA to move and as above, we couldn't think what we'd put in it. But for DC with more stuff it's a really efficient way to create a lot of easily accessible storage, if funds allow.