+static struct cell *map_stack_next(void)
+{
+ struct cell *tile = NULL;
+
+ while( !tile )
+ {
+ struct vframe *frame = &map.stack.frames[ map.stack.level ];
+
+ int output_dirs[][2] = { {0,-1}, {-1,0}, {1,0} };
+
+ if( frame->i < 3 )
+ {
+ int *dir = output_dirs[ frame->i ];
+ tile = map_tile_at( (int[2]){frame->x+dir[0], frame->y+dir[1]} );
+ frame->i ++;
+
+ if( tile && !(tile->flags & CELL_FLAG_VISITED) )
+ {
+ map.stack.level ++;
+ frame[1].i = 0;
+ frame[1].x = frame[0].x+dir[0];
+ frame[1].y = frame[0].y+dir[1];
+ }
+ else
+ tile = NULL;
+ }
+ else
+ {
+ map.stack.level --;
+ tile = NULL;
+
+ if( map.stack.level < 0 )
+ return NULL;
+ }
+ }
+
+ return tile;
+}
+
+static int map_load( const char *str )
+{
+ map_free();
+
+ char *c = str;
+
+ // Scan for width
+ for(;; map.x ++)
+ {
+ if( str[map.x] == ';' )
+ break;
+ else if( !str[map.x] )
+ {
+ vg_error( "Unexpected EOF when parsing level!\n" );
+ return 0;
+ }
+ }
+
+ struct cell *row = arraddnptr( map.cells, map.x );
+ int cx = 0;
+ int reg_start = 0, reg_end = 0;
+
+ for(;;)
+ {
+ if( !*c )
+ break;
+
+ if( *c == ';' )
+ {
+ c ++;
+
+ // Parse attribs
+ if( *c != '\n' )
+ {
+ while( *c )
+ {
+ if( reg_start < reg_end )
+ {
+ if( *c >= 'a' && *c <= 'z' )
+ {
+ arrpush( map.cells[ map.io[ reg_start ] ].conditions, *c );
+ }
+ else
+ {
+ if( *c == ',' || *c == '\n' )
+ {
+ reg_start ++;
+
+ if( *c == '\n' )
+ break;
+ }
+ else
+ {
+ vg_error( "Unkown attrib '%c' (row: %u)\n", *c, map.y );
+ return 0;
+ }
+ }
+ }
+ else
+ {
+ vg_error( "Over-assigned values (row: %u)\n", map.y );
+ return 0;
+ }
+
+ c ++;
+ }
+ }
+
+ if( reg_start != reg_end )
+ {
+ vg_error( "Not enough values assigned (row: %u, %u of %u)\n", map.y, reg_start, reg_end );
+ return 0;
+ }
+
+ if( cx != map.x )
+ {
+ vg_error( "Map row underflow (row: %u, %u<%u)\n", map.y, cx, map.x );
+ return 0;
+ }
+
+ row = arraddnptr( map.cells, map.x );
+ cx = 0;
+ map.y ++;
+ reg_end = reg_start = arrlen( map.io );
+ }
+ else
+ {
+ if( cx == map.x )
+ {
+ vg_error( "Map row overflow (row: %u, %u>%u)\n", map.y, cx, map.x );
+ return 0;
+ }
+
+ row[ cx ].conditions = NULL;
+
+ // Parse the various cell types
+ if( *c == '+' || *c == '-' )
+ {
+ arrpush( map.io, cx + map.y*map.x );
+ row[ cx ++ ].flags = *c == '+'? CELL_FLAG_INPUT: CELL_FLAG_OUTPUT;
+ reg_end ++;
+ }
+ else if( *c == '#' )
+ {
+ row[ cx ++ ].flags = CELL_FLAG_WALL;
+ }
+ else
+ {
+ row[ cx ++ ].flags = 0x00;
+ }
+ }
+
+ c ++;
+ }
+
+ // Origin top left corner
+ map.origin[0] = -((float)map.x) * 0.5f;
+ map.origin[2] = -((float)map.y) * 0.5f;
+
+ vg_success( "Map loaded! (%u:%u)\n", map.x, map.y );
+ return 1;
+}
+
+static int map_tile_availible( int co[2] )
+{
+ // Extract 5x5 grid surrounding tile
+ u32 blob = 0x1000;
+ for( int y = vg_max( co[1]-2, 0 ); y < vg_min( map.y, co[1]+3 ); y ++ )
+ for( int x = vg_max( co[0]-2, 0 ); x < vg_min( map.x, co[0]+3 ); x ++ )
+ {
+ struct cell *cell = map_tile_at( (int[2]){ x, y } );
+
+ if( cell && (cell->flags & CELL_FLAG_WALKABLE) )
+ blob |= 0x1 << ((y-(co[1]-2))*5 + x-(co[0]-2));
+ }
+
+ // Run filter over center 3x3 grid to check for invalid configurations
+ int kernel[] = { 0, 1, 2, 5, 6, 7, 10, 11, 12 };
+ for( int i = 0; i < vg_list_size(kernel); i ++ )
+ {
+ if( blob & (0x1 << (6+kernel[i])) )
+ {
+ // (reference window: 0x1CE7) Illegal moves
+ // 0100011100010 ;
+ // 0000001100011 ;
+ // 0000011000110 ;
+ // 0110001100000 ;
+ // 1100011000000 ;
+ // 0100001100010 ;
+ // 0100011000010 ;
+
+ u32 invalid[] = { 0x8E2, 0x63, 0xC6, 0xC60, 0x18C0, 0x862, 0x8C2 };
+ u32 window = blob >> kernel[i];
+
+ for( int j = 0; j < vg_list_size(invalid); j ++ )
+ if((window & invalid[j]) == invalid[j])
+ return 0;
+ }
+ }
+
+ return 1;