Winapi console and threading

I've been toying around with game ideas while trying to figure out threading; I've got a simple program and was hoping to get an idea on any problems that occur before I move on. Right now, it just moves the "enemies" about.

Code:

// compiled using Code::Blocks 10.05
// modified threading example
// http://www.cs.rpi.edu/academics/courses/netprog/WindowsThreads.html
// Win32 console app

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define MAX_E 15 // number of "enemies"
#define MAX_Y 20 // max rows
#define MAX_X 79 // max cols

HANDLE hcon;   // global handle to console window
int sentinel;  // global loop control variable

typedef struct {

    COORD old_c;
    COORD new_c;
    char shown;
    char blank;

    // structure for each "character"
} test;

typedef struct {

    test *enemies_list;

    // the thread function allows only one argument.  To pass a boat load
    // of data, use a struct as a "container" of other data
} enemy_array;

DWORD WINAPI ThreadRoutine(LPVOID lpArg) {

    enemy_array t = *(enemy_array *)lpArg;

    // lpArg needs to be cast to the appropriate data type
    // in this case, it's (enemy_array *).  To get to the data
    // we want, dereference *(cast_type *)lpArg

    for(; sentinel != 10; ) {

        // to exit out of the threading function,
        // set the sentinel value from within the main
        //     !! not sure if this is correct !!

        int i = 0;
        time_t t1 = time(0), t2;

        do{ t2 = time(0); } while(t2 < t1 + 1);

        // crude timer function; wait for ~1 second

        while(i < MAX_E) {

            SetConsoleCursorPosition(hcon, t.enemies_list[i].old_c);
            putchar(t.enemies_list[i].blank);

            // update each of the "enemies" by placing a space where it
            // was; there is NO collision detection at this time

            switch(rand() % 4) {
                case 0 : if(t.enemies_list[i].new_c.Y - 1 > 0) // move up
                            --t.enemies_list[i].new_c.Y;
                         else if(t.enemies_list[i].new_c.Y == 0)
                            t.enemies_list[i].new_c.Y = MAX_Y;
                         break;
                case 1 : if(t.enemies_list[i].new_c.X - 1 > 0) // move left
                            --t.enemies_list[i].new_c.X;
                         else if(t.enemies_list[i].new_c.X == 0)
                            t.enemies_list[i].new_c.X = MAX_X;
                         break;
                case 2 : if(t.enemies_list[i].new_c.X + 1 < MAX_X) // move right
                            ++t.enemies_list[i].new_c.X;
                         else if(t.enemies_list[i].new_c.X == MAX_X)
                            t.enemies_list[i].new_c.X = 0;
                         break;
                case 3 : if(t.enemies_list[i].new_c.Y + 1 < MAX_Y) // move down
                            ++t.enemies_list[i].new_c.Y;
                         else if(t.enemies_list[i].new_c.Y == MAX_Y)
                            t.enemies_list[i].new_c.Y = 0;
                         break;
             }

             SetConsoleCursorPosition(hcon, t.enemies_list[i].new_c);
             putchar(t.enemies_list[i].shown);

             t.enemies_list[i].old_c.X = t.enemies_list[i].new_c.X;
             t.enemies_list[i].old_c.Y = t.enemies_list[i].new_c.Y;

             // update the new coordinates of each "enemy"

             ++i;
        }
    }

	return NULL;
}

int main() {

	int i;
	HANDLE hHandles; // handle to thread
	DWORD ThreadId;
	CONSOLE_CURSOR_INFO cci; // structure for cursor

	test player = { { 40, 10 }, { 40, 10 }, 'X', ' ' };
	enemy_array ea;

	ea.enemies_list = malloc(sizeof(test) * MAX_E); // allocate some enemies

	if(ea.enemies_list) {
	    int i=0;

	    while(i < MAX_E) {
	        ea.enemies_list[i].blank = ' ';
	        ea.enemies_list[i].shown = "!@#$%^&*()_+"[rand() % 12];
	        ea.enemies_list[i].new_c.X = ea.enemies_list[i].old_c.X = rand() % 80;
	        ea.enemies_list[i].new_c.Y = ea.enemies_list[i].old_c.Y = rand() % 20;

	        // set their coordinates and assign them a "random" display character
	        ++i;
	    }
	} else {
	    fprintf(stderr, "could not allocate space for enemies");
	    return 1;
	}

	sentinel = 0; // controls the threading function runtime

    cci.dwSize = 1;
    cci.bVisible = 0; // hide the cursor

	hcon = GetStdHandle(STD_OUTPUT_HANDLE);  // get handle to console window
	SetConsoleCursorInfo(hcon, &cci);        // prepare display
	hHandles = CreateThread(NULL, 0, ThreadRoutine, &ea, 0, &ThreadId);
	// try to create the thread

	if (hHandles == NULL) {
	     fprintf(stderr,"Could not create Thread\n");
		 exit(0);
	}

	SetConsoleCursorPosition(hcon, player.new_c);
	putchar(player.shown);
	// set the initial placement of the player's character

	for(; getchar() != '\n';) {

	    // main player loop

	}

	sentinel = 10;

	// clean up and prepare for program termination

	WaitForSingleObject(hHandles, INFINITE);

	cci.dwSize = 1;
	cci.bVisible = 1;
	SetConsoleCursorInfo(hcon, &cci);
	// restore cursor

	free(ea.enemies_list);

	return 0;
}

If anyone sees anything troublesome, please point it out.