diff --git a/packages/ludic.minimap/explored.ludic b/packages/ludic.minimap/explored.ludic
index 1c847c9b..7668205a 100644
--- a/packages/ludic.minimap/explored.ludic
+++ b/packages/ludic.minimap/explored.ludic
@@ -74,17 +74,20 @@ function mm_land_count(minimap_st: mut MinimapState) -> void {
 # the ground under the grid is not what it was (a new world): count its land again
 export function minimap_land_changed(minimap_st: mut MinimapState) -> void { minimap_st.mm_land_n = 0 }
 
-# the grid as one string of 0 / 1, row by row, and back (a shorter string leaves the rest unseen)
-@alloc_ok("on a save: the explored grid written out")
+# the grid as one string of 0 / 1, row by row, and back (a shorter string leaves the rest unseen).
+# Written into bytes the state keeps (a string a cell before, every save): good until the next save
 export function minimap_seen_text(minimap_st: mut MinimapState) -> string {
   mm_grid(minimap_st)
-  var s = ""
-  for j in 0 .. minimap_st.mm_cells {
-    var row = ""
-    for i in 0 .. minimap_st.mm_cells { if minimap_st.mm_seen[j * minimap_st.mm_cells + i] != 0 { row = row + "1" } else { row = row + "0" } }
-    s = s + row
+  let n = minimap_st.mm_cells * minimap_st.mm_cells
+  if minimap_st.mm_seen_cap < n + 1 { mm_seen_buf_make(minimap_st, n + 1) }
+  let p = minimap_st.mm_seen_buf
+  unsafe {
+    for c in 0 .. n {
+      if minimap_st.mm_seen[c] != 0 { p[c] = 49 } else { p[c] = 48 }
+    }
+    p[n] = 0
   }
-  return s
+  return p
 }
 
 export function minimap_seen_from_text(minimap_st: mut MinimapState, s: string) -> void {
diff --git a/packages/ludic.minimap/grid.ludic b/packages/ludic.minimap/grid.ludic
index de4e15e1..9fcb76eb 100644
--- a/packages/ludic.minimap/grid.ludic
+++ b/packages/ludic.minimap/grid.ludic
@@ -1,6 +1,8 @@
 # grid.ludic - the explored grid: square cells round the origin, and the part of it "explored" is
 # measured over (a core, so a bigger grid does not change what a share of it means)
 export state MinimapState {
+  mm_seen_buf: pointer = null   # minimap_seen_text's bytes, kept and written again on every save
+  mm_seen_cap: int = 0
   mm_none: MinimapPin = new MinimapPin   # minimap_pin past the end: an empty mark, the same one each time
   mm_near: []int = new []int    # minimap_pins_near's answer, cleared and refilled: a compass asks every frame
   mm_land_n: int = 0            # land cells in the core, counted once per origin
@@ -78,3 +80,13 @@ export function minimap_cell(minimap_st: MinimapState, x: float, z: float) -> in
 }
 
 function mm_grid(minimap_st: mut MinimapState) -> void { if minimap_st.mm_seen == null { minimap_config(minimap_st, minimap_st.mm_cells, minimap_st.mm_cell_m) } }
+
+@alloc_ok("once per grid size: the save's bytes, kept")
+function mm_seen_buf_make(minimap_st: mut MinimapState, cap: int) -> void {
+  let old = minimap_st.mm_seen_buf
+  unsafe {
+    if old != null { free(old) }
+    minimap_st.mm_seen_buf = bytes(cap)
+  }
+  minimap_st.mm_seen_cap = cap
+}