How to draw an euqilateral triangle.

Hey, I've been at this for a few days now and I cannot for the life of me figure this one out.
I need to draw a trinagle with "*" and "-" that looks like this

*--------
**-------
***------
****-----
*****----
****-----
***------
**-------
*--------
it doesn't look like it in the picture but the picture is supposed to be a complete square with and odd number of rows and columns.
I am at my wit's end on this. I don't even know how to begin on this. In the rest of my program I have already used FOR loops to draw other types of triangles, but this one is just killing me. Thank you for any help. It is greatly appreciated.

this may be a messy way but I'ts the best I can do at this time of night

Code:

#include <stdio.h>

int main()
{
	int star, dash, x;
	
	star = 1;
	dash = 8;

	while(star<6)
	{
		for(x = 0; x < star; x++)
			putchar('*');
		for(x = 0; x < dash; x++)
			putchar('-');

		putchar('\n');
		star++;
		dash--;
	}

	star = 4;
	dash = 5;

	while(star>0)
	{
		for(x = 0; x < star; x++)
			putchar('*');
		for(x = 0; x < dash; x++)
			putchar('-');

		putchar('\n');
		star--;
		dash++;
	}
	return 0;
}

You can probably improve this, I'll leave that up to you as you should do some homework