From 424f2ccbf620ab993486d51fdb48c6c300d8fc1b Mon Sep 17 00:00:00 2001
From: Jason Hilder <jhilder95@gmail.com>
Date: Mon, 3 Aug 2026 06:41:31 +0200
Subject: [PATCH] Small tweaks and cleanup to flow field.

---
 src/map.odin | 55 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/src/map.odin b/src/map.odin
index 94a865b..a67f9c7 100644
--- a/src/map.odin
+++ b/src/map.odin
@@ -185,7 +185,6 @@ check_map_collision :: proc(rect: rl.Rectangle, game_map: Game_Map) -> bool {
 
 // true when collision found
 check_enemy_collision :: proc(rect_a: rl.Rectangle, active_enemies: int, enemies: ^[MAX_ENEMIES]Enemy) -> bool {
-
     for idx in 0..<active_enemies {
         e := enemies[idx]
         enemy_rect := get_enemy_collider(e, e.position)
@@ -222,6 +221,9 @@ draw_map :: proc(current_map: Game_Map) {
 	}
 }
 
+// ----------------------------------------------------------
+// FLOW FIELD IMPL
+// ----------------------------------------------------------
 reset_cost_array :: proc(cost_arr: ^[400]int) {
 	for val, idx in cost_arr {
 		cost_arr[idx] = -1
@@ -253,6 +255,25 @@ compute_flow_field :: proc(game_map: ^Game_Map, player_pos: rl.Vector2) {
 
                 nx := current.x + loop_x
                 ny := current.y + loop_y
+
+                // diagonal — check flanking orthogonal tiles before allowing expansion
+                if loop_x != 0 && loop_y != 0 {
+                    flank_a := Grid_Pos{current.x + loop_x, current.y}
+                    flank_b := Grid_Pos{current.x, current.y + loop_y}
+
+                    // @TODO VISUALIZE + UNDERSTAND THIS CONCEPTUALLY
+                    if flank_a.x >= 0 && flank_a.x < game_map.width && flank_a.y >= 0 && flank_a.y < game_map.height &&
+                    flank_b.x >= 0 && flank_b.x < game_map.width && flank_b.y >= 0 && flank_b.y < game_map.height {
+                        flank_a_idx := grid_to_index(flank_a.x, flank_a.y, game_map.width)
+                        flank_b_idx := grid_to_index(flank_b.x, flank_b.y, game_map.width)
+                        flank_a_tile := Tile_Type(game_map.data[flank_a_idx])
+                        flank_b_tile := Tile_Type(game_map.data[flank_b_idx])
+                        if tile_defs[flank_a_tile].solid || tile_defs[flank_b_tile].solid {
+                            continue // corner-cutting diagonal, don't expand BFS through it
+                        }
+                    }
+                }
+
 				get_neighbor_cost({nx, ny}, &flow_field_queue, game_map, current_cost)
             }
         }
@@ -277,10 +298,11 @@ get_neighbor_cost :: proc(grid_pos: Grid_Pos, queue: ^[dynamic]Grid_Pos, game_ma
 compute_flow_directions :: proc(game_map: ^Game_Map) {
 	// walk every tile, look at neighbor costs in cost_field,
 	// write a direction vector into direction_field[index]
-	for value, index in game_map.data {
+	for _, index in game_map.data {
 		row := index / game_map.width
 		column := index % game_map.width
-		current_index := grid_to_index(column, row, game_map.width)
+		// current_index := grid_to_index(column, row, game_map.width)
+		current_index := index
 
 		// skip unreachable tiles
 		if game_map.cost_field[current_index] == -1 do continue
@@ -306,6 +328,33 @@ compute_flow_directions :: proc(game_map: ^Game_Map) {
 					cost_index := grid_to_index(ncolumn, nrow, game_map.width)
                     neighbor_cost := game_map.cost_field[cost_index]
 
+                    // we have the lowest neighbor at this point.
+                    // Check if its diagonal first
+                    // compare the neighbor to the current tile to check the diff, it will tell if diagonal
+                    // Diagonal moves cut through a "corner" formed by two orthogonal tiles.
+                    // Before allowing one, check both flank tiles (the up/down one + the left/right one).
+                    // If either is solid, the diagonal is blocked — even if the target tile itself is open.
+                    if ncolumn - column != 0 && nrow - row != 0 {
+                        // no axis is 0 so we have an angle 
+                        // diagonal — check the two flanking orthogonal neighbors
+                        flank_a_col := column + (ncolumn - column) // same x-offset, y unchanged
+                        flank_a_row := row
+                        flank_b_col := column
+                        flank_b_row := row + (nrow - row)          // same y-offset, x unchanged
+
+                        flank_a_idx := grid_to_index(flank_a_col, flank_a_row, game_map.width)
+                        flank_b_idx := grid_to_index(flank_b_col, flank_b_row, game_map.width)
+
+                        flank_a_tile := Tile_Type(game_map.data[flank_a_idx])
+                        flank_b_tile := Tile_Type(game_map.data[flank_b_idx])
+
+                        if tile_defs[flank_a_tile].solid || tile_defs[flank_b_tile].solid {
+							// corner-cutting diagonal, disqualify — skip to next neighbor in the loop
+                            continue 
+                        }
+
+                    }
+
     				if neighbor_cost != -1 && neighbor_cost < lowest_cost {
                         lowest_cost = neighbor_cost
                         b = rl.Vector2{f32(ncolumn), f32(nrow)}