+ static int compute_flow_counter = 0;
+ compute_flow_counter ^= 0x1;
+
+ for( int i = 0; i < map.y*map.x; i ++ )
+ {
+ struct cell *cell = map.cells + i;
+
+ cell->flowing[compute_flow_counter] = cell->flowing[compute_flow_counter^0x1];
+
+ if( !map.cells[i].source_count )
+ cell->flowing[ compute_flow_counter ] = vg_max( cell->flowing[ compute_flow_counter ] - 10, 0 );
+
+ map.cells[i].source_count = 0;
+ }
+
+ for( int y = 0; y < map.y; y ++ )
+ {
+ for( int x = 0; x < map.x; x ++ )
+ {
+ struct cell *cur = map.cells + y*map.x + x;
+ u8 *cellbytes = celldata + (y*map.x+x)*4;
+
+ if( cur->flags & CELL_FLAG_WALKABLE )
+ {
+ struct cell *a, *b, *c, *d;
+
+ a = map_tile_at_cond( (int[2]){ x,y+1 }, CELL_FLAG_WALKABLE );
+ b = map_tile_at_cond( (int[2]){ x+1,y }, CELL_FLAG_WALKABLE );
+ c = map_tile_at_cond( (int[2]){ x,y-1 }, CELL_FLAG_WALKABLE );
+ d = map_tile_at_cond( (int[2]){ x-1,y }, CELL_FLAG_WALKABLE );
+
+ u32 config = (a?0x1:0x0) | (b?0x2:0x0) | (c?0x4:0x0) | (d?0x8:0x0);
+ cellbytes[ 0 ] = config;
+
+ if( cur->flags & CELL_FLAG_OUTPUT )
+ cur->flowing[ compute_flow_counter ] = 128;
+ }
+ else
+ {
+ // TODO: Random background tiles
+ cellbytes[ 0 ] = 1;
+ }
+ }
+ }
+
+ int const k_rate_flow = 16;
+
+ map_stack_refresh();
+ for( int i = 0; i < arrlen( map.io ); i ++ )
+ {
+ int inputcoord[2];
+ if( map.cells[ map.io[i] ].flags & CELL_FLAG_OUTPUT )
+ {
+ map_tile_coords_from_index( map.io[i], inputcoord );
+ map_stack_init( inputcoord );
+ struct cell *cell = map_tile_at( inputcoord );
+
+ int cr[2];
+
+ do
+ {
+ map_stack_current_coords( cr, 0 );
+
+ u8 *cellbytes = celldata + (cr[1]*map.x+cr[0])*4;
+
+ int outflow = cell->flowing[ compute_flow_counter ^ 0x1 ];
+ int sourcing = outflow? 1: 0;
+ int outrate = outflow == 128? k_rate_flow: 0;
+
+ struct cell *a, *b, *d;
+ a = map_tile( (int[2]){ cr[0], cr[1]+1 } );
+ b = map_tile( (int[2]){ cr[0]+1, cr[1] } );
+ d = map_tile( (int[2]){ cr[0]-1, cr[1] } );
+
+ int compute_l = 0, compute_r = 0;
+
+ switch( cellbytes[0] )
+ {
+ // DOWN
+ case 1: case 5: case 11: case 9: case 3:
+ a->flowing[ compute_flow_counter ] += outrate;
+ a->source_count += sourcing;
+ break;
+ case 2: case 6: compute_r = 1; break;
+ case 8: case 12: compute_l = 1; break;
+ case 10: case 14: compute_l = 1; compute_r = 1; break;
+ default: break;
+ }
+
+ if( compute_r && (celldata[ (cr[1]*map.x+cr[0]+1)*4 ] != 14) )
+ {
+ b->flowing[ compute_flow_counter ] += outrate;
+ b->source_count += sourcing;
+ }
+
+ if( compute_l && (celldata[ (cr[1]*map.x+cr[0]-1)*4 ] != 14) )
+ {
+ d->flowing[ compute_flow_counter ] += outrate;
+ d->source_count += sourcing;
+ }
+
+ if( cellbytes[0] == 10 )
+ {
+ int crl[2];
+ map_stack_current_coords( crl, -1 );
+
+ if( crl[0] < cr[0] )
+ {
+ cellbytes[0] = 15;
+ }
+ }
+ }
+ while( (cell = map_stack_next()) );
+ }
+ }
+
+ for( int i = 0; i < map.y*map.x; i ++ )