diff --git a/crystal.cpp b/crystal.cpp
index a21cfe20..cabc916c 100644
--- a/crystal.cpp
+++ b/crystal.cpp
@@ -1318,9 +1318,7 @@ EX void set_crystal(int sides) {
   set_variation(eVariation::pure);
   ginf[gCrystal].sides = sides;
   ginf[gCrystal].vertex = 4;
-  static char buf[20];
-  sprintf(buf, "{%d,4}", sides);
-  ginf[gCrystal].tiling_name = buf;
+  ginf[gCrystal].tiling_name = hr::format("{%d,4}", sides);
   ginf[gCrystal].distlimit = distlimit_table[min(sides, MAX_EDGE_CRYSTAL-1)];
   }
 
diff --git a/debug.cpp b/debug.cpp
index c230b40c..9b1aba99 100644
--- a/debug.cpp
+++ b/debug.cpp
@@ -308,8 +308,6 @@ struct debugScreen {
       #if CAP_SHAPES
       queuepoly(gmatrix[what], cgi.shAsymmetric, 0x80808080);
       #endif
-      char buf[200];
-      sprintf(buf, "%p", hr::voidp(what));
       dialog::addSelItem("mpdist", its(what->mpdist), 'd');
       dialog::add_action([what] () { 
         bitfield_editor(what->mpdist, [what] (int i) { what->mpdist = 0; }, "generation level");        
@@ -390,7 +388,7 @@ struct debugScreen {
       dialog::addBreak(50);
       
       if(show_debug_data) {
-        dialog::addSelItem("pointer", s0+buf+"/"+index_pointer(what), 0);
+        dialog::addSelItem("pointer", s0+hr::format("%p", hr::voidp(what))+"/"+index_pointer(what), 0);
         dialog::addSelItem("cpdist", its(what->cpdist), 0);
         dialog::addSelItem("celldist", its(celldist(what)), 0);
         dialog::addSelItem("celldistance", its(celldistance(cwt.at, what)), 0);
diff --git a/help.cpp b/help.cpp
index fcdeb014..150f8b95 100644
--- a/help.cpp
+++ b/help.cpp
@@ -586,8 +586,7 @@ EX string generateHelpForWall(eWall w) {
 void buteol(string& s, int current, int req) {
   int siz = isize(s);
   if(s[siz-1] == '\n') s.resize(siz-1);
-  char buf[100]; sprintf(buf, " (%d/%d)", current, req);
-  s += buf; s += "\n";
+  s += hr::format(" (%d/%d)\n", current, req);
   }
 
 EX string generateHelpForMonster(eMonster m) {
@@ -930,7 +929,7 @@ EX void describeMouseover() {
       }
 
     if(buggyGeneration) {
-      char buf[80]; sprintf(buf, " %p H=%d M=%d", hr::voidp(c), c->landparam, c->mpdist); out += buf;
+      out += hr::format(" %p H=%d M=%d", hr::voidp(c), c->landparam, c->mpdist);
       }
     
     if(randomPatternsMode)
diff --git a/history.cpp b/history.cpp
index 14ef4eb0..d89feaff 100644
--- a/history.cpp
+++ b/history.cpp
@@ -498,10 +498,7 @@ EX namespace history {
           
           pushScreen(progress_screen);
   
-          char buf[128];
-          sprintf(buf, "#%03d", segid);
-  
-          progress(s0 + buf + " ("+its(j+bonus)+"/"+its(siz+bonus+bonus-1)+")"); */
+          progress(s0 + hr::format("#%03d (%d/%d)", segid, j+bonus, siz+bonus+bonus-1)); */
   
           // calcparam(); current_display->radius = bandhalf;
           phase = j; movetophase();
diff --git a/hprint.cpp b/hprint.cpp
index f48e21a2..55aeb794 100644
--- a/hprint.cpp
+++ b/hprint.cpp
@@ -33,9 +33,9 @@ EX int debugflags = DF_INIT | DF_ERROR | DF_WARN | DF_MSG | DF_TIME | DF_LOG;
 
 EX string s0;
 
-EX string its(int i) { char buf[64]; sprintf(buf, "%d", i); return buf; }
+EX string its(int i) { return hr::format("%d", i); }
 
-EX string itsh8(int i) {static char buf[16]; sprintf(buf, "%08X", i); return buf; }
+EX string itsh8(int i) { return hr::format("%08X", i); }
 
 EX string fts(ld x, int prec IS(6)) {
   std::stringstream ss;
@@ -399,9 +399,9 @@ EX string llts(long long i) {
     if(i < 10) return its((int) i);
     return llts(i/10) + its(i%10);
 }
-EX string itsh(unsigned int i) {static char buf[16]; sprintf(buf, "%03X", i); return buf; }
-EX string itsh(int i) {static char buf[16]; sprintf(buf, "%03X", i); return buf; }
-EX string itsh2(int i) {static char buf[16]; sprintf(buf, "%02X", i); return buf; }
+EX string itsh(unsigned int i) { return hr::format("%03X", i); }
+EX string itsh(int i) { return hr::format("%03X", i); }
+EX string itsh2(int i) { return hr::format("%02X", i); }
 
 EX string itsh(unsigned long long i) {
   int i0 = int(i);
@@ -483,9 +483,7 @@ template<class T> T deserialize(const string& s) {
 EX string as_hexstring(string o) {
   string res;
   for(char x: o) {
-    char buf[4];
-    sprintf(buf, "%02X", (unsigned char)(x));
-    res += buf;
+    res += hr::format("%02X", (unsigned char)(x));
     }
   return res;
   }
diff --git a/mobile.cpp b/mobile.cpp
index c304aaae..8cd88078 100644
--- a/mobile.cpp
+++ b/mobile.cpp
@@ -26,15 +26,13 @@ string buildScoreDescription() {
 
   for(int i=0; i<ittypes; i++) if(items[i]) {
     string t = XLATN(iinf[i].name);
-    sprintf(buf2, " %s (%d)", t.c_str(), items[i]);
-    s += buf2;
+    s += hr::format(" %s (%d)", t.c_str(), items[i]);
     }
   s += "\n";
   s += XLAT("Kills: ") + its(tkills());
   for(int i=1; i<motypes; i++) if(kills[i]) {
     string t = XLATN(minf[i].name);
-    sprintf(buf2, " %s (%d)", t.c_str(), kills[i]);
-    s += buf2;
+    s += hr::format(" %s (%d)", t.c_str(), kills[i]);
     }
   s += "\n";
 
diff --git a/netgen.cpp b/netgen.cpp
index 46276879..b836b36c 100644
--- a/netgen.cpp
+++ b/netgen.cpp
@@ -439,9 +439,7 @@ EX namespace netgen {
     for(int ix=0; ix<PX; ix++) {
       for(int y=0; y<qy; y++) for(int x=0; x<qx; x++)
         qpixel(quarter,x,y) = qpixel(net, x+qx*ix, y+qy*iy);
-      char buf[64];
-      sprintf(buf, "papermodel-page%d%d" IMAGEEXT, iy, ix);
-      IMAGESAVE(quarter, buf);
+      IMAGESAVE(quarter, hr::format("papermodel-page%d%d" IMAGEEXT, iy, ix).c_str());
       }
     
     SDL_FreeSurface(net);
diff --git a/quit.cpp b/quit.cpp
index 02a80817..828e9c8d 100644
--- a/quit.cpp
+++ b/quit.cpp
@@ -27,9 +27,7 @@ EX int getgametime() {
   }
 
 EX string getgametime_s(int timespent IS(getgametime())) {
-  char buf[20];
-  sprintf(buf, "%d:%02d", timespent/60, timespent % 60);
-  return buf;
+  return hr::format("%d:%02d", timespent/60, timespent % 60);
   }
 
 EX bool display_yasc_codes;
diff --git a/rogueviz/collatz.cpp b/rogueviz/collatz.cpp
index 5b01810b..c371f895 100644
--- a/rogueviz/collatz.cpp
+++ b/rogueviz/collatz.cpp
@@ -274,7 +274,7 @@ struct storydata { int s; int e; const char *text; } story[] = {
 #undef T
 #endif
 
-string its05(int i) { char buf[64]; sprintf(buf, "%05d", i); return buf; }
+string its05(int i) { return hr::format("%05d", i); }
 
 int dimid(char x) {
   if(x >= 'a' && x < 'a' + GDIM) return x - 'a';
diff --git a/rogueviz/dhrg/visualize.cpp b/rogueviz/dhrg/visualize.cpp
index 457fd77a..6846e4e0 100644
--- a/rogueviz/dhrg/visualize.cpp
+++ b/rogueviz/dhrg/visualize.cpp
@@ -29,13 +29,12 @@ void show_likelihood() {
     for(int i=0; i<MAXDIST; i++) bonus_tally[i] = 0;
 
   for(int u=0; u<MAXDIST; u++) if(tally[u] || bonus_tally[u]) {
-    char buf[20];
-    sprintf(buf, "%.6lf", lc_type == 'R' ? current_logistic.yes(u) : double(edgetally[u] * 1. / tally[u]));    
+    string value = hr::format("%.6lf", lc_type == 'R' ? current_logistic.yes(u) : double(edgetally[u] * 1. / tally[u]));
     string s = its(u);
     if(isize(s) == 1) s = "0" + s;
     s += ": " + its(edgetally[u]) + " / " + its(tally[u]);
     if(bonus_tally[u]) s += " [" + its(bonus_edgetally[u]) + "/" + its(bonus_tally[u]) + "]";
-    dialog::addSelItem(s, buf, 0);
+    dialog::addSelItem(s, value, 0);
     }
   
   char letters[3] = {'O', 'R', 'M'};
diff --git a/screenshot.cpp b/screenshot.cpp
index e692143b..6362f247 100644
--- a/screenshot.cpp
+++ b/screenshot.cpp
@@ -53,13 +53,13 @@ EX always_false in;
     static int id;
     id++; id %= 10;
     if(divby == 1) {
-      sprintf(buf[id], "%d", val); return buf[id];
+      snprintf(buf[id], 20, "%d", val); return buf[id];
       }
     else if(divby <= 10) {
-      sprintf(buf[id], "%.1f", val*1./divby); return buf[id];
+      snprintf(buf[id], 20, "%.1f", val*1./divby); return buf[id];
       }
     else {
-      sprintf(buf[id], "%.2f", val*1./divby); return buf[id];
+      snprintf(buf[id], 20, "%.2f", val*1./divby); return buf[id];
       }
     }
   
@@ -78,7 +78,7 @@ EX always_false in;
       else fill = 0xFFFFFFFF;
       }
     
-    sprintf(buf, "style=\"stroke:#%06x;stroke-opacity:%.3" PLDF ";stroke-width:%" PLDF "px;fill:#%06x;fill-opacity:%.3" PLDF "\"",
+    snprintf(buf, 600, "style=\"stroke:#%06x;stroke-opacity:%.3" PLDF ";stroke-width:%" PLDF "px;fill:#%06x;fill-opacity:%.3" PLDF "\"",
       (stroke>>8) & 0xFFFFFF, cta(stroke),
       width/divby,
       (fill>>8) & 0xFFFFFF, cta(fill)