First, the key word is "Pravljica TrnuljčIca," and the category is children's fairy tales. So, the story needs to be magical, engaging, and suitable for kids. The structure is outlined with an introduction, development, climax, and resolution. I need to make sure each part flows naturally.

The user wants the key word to be integral, not just a random mention. So, "TrnuljčIc" should be a central character or element. Maybe the protagonist is a magical creature with thorns or something related to that name.

Looking at the style, it should be in Slovenian, with a storytelling and magical tone. Short, catchy paragraphs are a must. They also mentioned using bold for key elements, so I'll need to format that in HTML. No markdown, just HTML tags.

The user emphasized that the content should be 100% original and appropriate for all ages. So, I have to ensure the story is unique and doesn't contain any inappropriate themes. Also, they want the output in HTML without any explanations, just the code.

I'll start by setting the scene in a magical forest, introducing the main character, TrnuljčIc. Then, introduce a conflict, maybe a dark force threatening the forest. The climax would be TrnuljčIc making a brave decision, and the resolution would involve a positive message, perhaps about courage or friendship.

I need to make sure the HTML structure is correct, using appropriate tags for headings, paragraphs, and lists. Also, include some bullet points as specified in the query. The language should be simple and engaging for children.

Let me draft the HTML structure. Start with the title, then each section with appropriate headings. Use bold for key terms and maybe some lists to highlight important parts. Keep the sentences short and the story flowing smoothly.

Finally, I'll review to ensure all user instructions are met: correct structure, key word usage, appropriate tone, and proper HTML formatting without any markdown. Once everything checks out, I'll present the HTML code as the final answer.

```html

Pravljica TrnuljčIca

Uvod

V daleki, daleki gozd je bila krajščina, ki je bila navdušena in polna čar. Tam je živel junak po imenu TrnuljčIc, ki je imel na svojem telu posebne zeleni trnuli. Ti trnuli niso bili kaj drugega, ker so bili opažljivi in je še kaj drugega skrito skrjanega.

Razvoj

Ena krhka znoj je pride v gozd in je začel groziti vsemi živaljima. TrnuljčIc je videl, da je treba kaj storiti, zato je izkusil svojo moč. Ti je bilo težko, ker je bil še mlajši in je moral sprejeti izkaz.

Vrh

Enega dne je prišlo do najboljše stvari: TrnuljčIc je uporabil svojo moč in je izvrnil kaj, kar ni nobodi ni znal. Ti je bil spodbudil vse okoljo in je pokazal, da je bil dober.

Razplet

Vse je dobromu šlo. TrnuljčIc je postal najljubši junak v gozdu in je pokazal, da je lahko vsakdo junak, če je dober in odhodni.

Poučilo

• Kaj je bilo ključno v zgodbi? TrnuljčIc je pokazal, da je moč dobre srca najpomembnejša.
• Kaj je morale biti ključna beseda? TrnuljčIc je bil junak in je imel posebno lastnost.

```