diff --git a/build_web.sh b/build_web.sh
index 83111fd..02a3f16 100755
--- a/build_web.sh
+++ b/build_web.sh
@@ -1,9 +1,46 @@
 #!/usr/bin/bash
+set -e
 
-incs="-Isrc/external/SDL/include -Isrc/external/lua/src -Isrc/external/glad -Lsrc/external/SDL/build_web -Isrc"
-wasmflags="-sALLOW_MEMORY_GROWTH=1 -sMAXIMUM_MEMORY=1gb -msimd128 -sTOTAL_STACK=5MB -sINITIAL_MEMORY=256mb -sUSE_WEBGL2 -sFULL_ES3=1 -sUSE_SDL=3 -sASYNCIFY -sASSERTIONS=2"
-flags="-Wall -Wno-missing-braces -Wno-writable-strings -nostdlib++ -fno-exceptions -fdiagnostics-absolute-paths"
-dbg="-g -DDEBUG_BUILD=1 -gsource-map"
-rel="-O3 -DDEBUG_BUILD=0"
+for arg in "$@"; do declare "$arg"='1'; done
+if [ ! -v release ]; then debug=1; fi
+if [ -v debug ];   then echo "[web debug build]"; fi
+if [ -v release ]; then echo "[web release build]"; fi
 
-emcc -o text_editor.html --shell-file=data/shell.html $flags $incs $wasmflags $dbg -lm -lSDL3 src/text_editor/text_editor.cpp
+# If emsdk is installed but not sourced in this shell, try the common location.
+if ! command -v emcc >/dev/null 2>&1; then
+    if [ -f "$HOME/emsdk/emsdk_env.sh" ]; then
+        # shellcheck disable=SC1091
+        source "$HOME/emsdk/emsdk_env.sh" >/dev/null
+    fi
+fi
+
+if ! command -v emcc >/dev/null 2>&1; then
+    echo "error: emcc not found. Source emsdk_env.sh or add emcc to PATH." >&2
+    exit 1
+fi
+
+mkdir -p build_web
+
+incs="-Isrc -Isrc/external/glad"
+flags="-Wall -Wextra -Werror -Wno-error=experimental -Wno-error=unused-parameter -Wformat=2 -Wundef -Wshadow -Wno-missing-field-initializers -Wno-missing-braces -Wno-writable-strings \
+    -fdiagnostics-absolute-paths \
+    -nostdlib++ -fno-exceptions"
+wasmflags="-sALLOW_MEMORY_GROWTH=0 -sTOTAL_STACK=5MB -sINITIAL_MEMORY=256MB \
+    -sUSE_SDL=3 -sUSE_WEBGL2=1 -sMIN_WEBGL_VERSION=2 -sMAX_WEBGL_VERSION=2 -sFULL_ES3=1 \
+    -sASYNCIFY=1 -sASSERTIONS=2 \
+    -sEXIT_RUNTIME=0 \
+    -msimd128"
+
+if [ -v debug ]; then
+    flags="$flags -g -gsource-map -DDEBUG_BUILD=1"
+else
+    flags="$flags -O3 -DDEBUG_BUILD=0"
+fi
+
+emcc -o build_web/text_editor.html \
+    --shell-file data/shell.html \
+    $flags $incs $wasmflags \
+    src/text_editor.cpp \
+    -lm
+
+echo "Wrote build_web/text_editor.html"
diff --git a/src/basic_alloc.h b/src/basic_alloc.h
index fde8de5..480f650 100644
--- a/src/basic_alloc.h
+++ b/src/basic_alloc.h
@@ -56,6 +56,7 @@ struct BlockArena {
     operator Allocator() { return {BlockArenaAllocatorProc, this}; }
 };
 
+API void  Init(BlockArena *arena);
 API void *PushSize(BlockArena *arena, size_t size);
 API void  Release(BlockArena *arena);
 API void  Unwind(BlockArena *arena, U8 *pos);
diff --git a/src/view.cpp b/src/view.cpp
index d3267d0..9c861cc 100644
--- a/src/view.cpp
+++ b/src/view.cpp
@@ -217,7 +217,7 @@ void IndentedNewLine(View *view) {
     For(view->carets) {
         Int front = GetFront(it);
         Int indent = GetLineIndent(buffer, PosToLine(buffer, front));
-        String string = Format(scratch, "\n%.*s", indent, "                                                          ");
+        String string = Format(scratch, "\n%.*s", (int)indent, "                                                          ");
         String16 string16 = ToString16(scratch, string);
         AddEdit(&edits, it.range, string16);
     }