diff --git a/build_web.sh b/build_web.sh
index 74c689d..03c5976 100755
--- a/build_web.sh
+++ b/build_web.sh
@@ -29,37 +29,57 @@ fi
 
 echo "=== Step 1: Compiling raylib for web ==="
 
-# Compile raylib source files
-emcc -c "$RAYLIB_DIR/src/rcore.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rcore.o"
-emcc -c "$RAYLIB_DIR/src/rshapes.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rshapes.o"
-emcc -c "$RAYLIB_DIR/src/rtextures.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rtextures.o"
-emcc -c "$RAYLIB_DIR/src/rtext.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rtext.o"
-emcc -c "$RAYLIB_DIR/src/rmodels.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rmodels.o"
-emcc -c "$RAYLIB_DIR/src/raudio.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/raudio.o"
+# raylib rarely changes; skip the (slow) rebuild if the archive already exists.
+# Delete "$RAYLIB_BUILD/libraylib.a" to force a clean raylib rebuild.
+if [ ! -f "$RAYLIB_BUILD/libraylib.a" ]; then
+    # Compile raylib source files
+    emcc -c "$RAYLIB_DIR/src/rcore.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rcore.o"
+    emcc -c "$RAYLIB_DIR/src/rshapes.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rshapes.o"
+    emcc -c "$RAYLIB_DIR/src/rtextures.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rtextures.o"
+    emcc -c "$RAYLIB_DIR/src/rtext.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rtext.o"
+    emcc -c "$RAYLIB_DIR/src/rmodels.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/rmodels.o"
+    emcc -c "$RAYLIB_DIR/src/raudio.c" $RAYLIB_CFLAGS -o "$RAYLIB_BUILD/raudio.o"
 
-# Create static library
-cd "$RAYLIB_BUILD"
-emar rcs libraylib.a rcore.o rshapes.o rtextures.o rtext.o rmodels.o raudio.o
+    # Create static library
+    cd "$RAYLIB_BUILD"
+    emar rcs libraylib.a rcore.o rshapes.o rtextures.o rtext.o rmodels.o raudio.o
+    cd "$SCRIPT_DIR"
+else
+    echo "libraylib.a found, skipping raylib rebuild"
+fi
+
+# Compile the application modules (web version — no subprocess support).
+# platform_web.c provides stub implementations for spawn/error functions.
+# Keep this list in sync with rspektrum.make (use platform_web instead of
+# platform_linux for the web target).
+echo "=== Step 2: Compiling spectrogram modules for web ==="
 cd "$SCRIPT_DIR"
 
-# Compile spectrogram (web version — no subprocess support)
-# platform_web.c provides stub implementations for spawn/error functions
-echo "=== Step 2: Compiling spectrogram + platform for web ==="
-cd "$SCRIPT_DIR"
+APP_MODULES="spectrogram fft stft audio render ui utils primitives platform_web"
 
-# Compile platform_web.o (handles fork/execvp stubs for web)
-emcc -c -Os -Wall -DPLATFORM_WEB "$SRC_DIR/platform_web.c" -o "$RAYLIB_BUILD/platform_web.o"
+APP_OPT="-Os"
+if [ "$BUILD_TYPE" = "debug" ]; then
+    APP_OPT="-g -O0"
+fi
 
-# Compile spectrogram
-emcc -c -Os -Wall -DPLATFORM_WEB "$SRC_DIR/spectrogram.c" \
-    -I"$RAYLIB_DIR/src" \
-    -I"$RAYLIB_DIR/src/external" \
-    -I"$RAYLIB_DIR/src/external/glfw/include" \
-    -Iinclude \
-    -o "$RAYLIB_BUILD/spectrogram.o"
+APP_INCLUDES="-I$RAYLIB_DIR/src -I$RAYLIB_DIR/src/external -I$RAYLIB_DIR/src/external/glfw/include -Iinclude"
+
+# NOTE: do NOT pass -DPLATFORM_WEB to the app modules. Our code selects web
+# behavior by linking platform_web.c (not via the macro), and PLATFORM_WEB is
+# also an enumerator in platform.h — defining it as a macro breaks that enum.
+# (raylib itself is built with -DPLATFORM_WEB above; it needs the macro.)
+OBJECTS=""
+for m in $APP_MODULES; do
+    echo "  CC $m.c"
+    emcc -c $APP_OPT -Wall $APP_INCLUDES \
+        "$SRC_DIR/$m.c" -o "$RAYLIB_BUILD/$m.o"
+    OBJECTS="$OBJECTS $RAYLIB_BUILD/$m.o"
+done
 
 # Linker flags
-LDFLAGS="-s USE_GLFW=3 -s ASYNCIFY -s TOTAL_MEMORY=67108864 -s FORCE_FILESYSTEM=1 --preload-file resources@resources --preload-file fonts/DejaVuSansMono.ttf@fonts/DejaVuSansMono.ttf --shell-file $SCRIPT_DIR/web_shell.html -s NO_EXIT_RUNTIME=1"
+# The font lives at resources/fonts/DejaVuSansMono.ttf and is loaded relative to
+# the resources dir at runtime, so the resources@resources preload covers it.
+LDFLAGS="-s USE_GLFW=3 -s ASYNCIFY -s TOTAL_MEMORY=67108864 -s FORCE_FILESYSTEM=1 --preload-file resources@resources --shell-file $SCRIPT_DIR/web_shell.html -s NO_EXIT_RUNTIME=1"
 
 if [ "$BUILD_TYPE" = "debug" ]; then
     LDFLAGS="$LDFLAGS -g -O0 -s ASSERTIONS=1"
@@ -69,13 +89,11 @@ fi
 
 # Compile and link
 emcc -o "$OUTPUT" \
-    "$RAYLIB_BUILD/platform_web.o" \
-    "$RAYLIB_BUILD/spectrogram.o" \
+    $OBJECTS \
     -I"$RAYLIB_DIR/src" \
     -I"$RAYLIB_DIR/src/external" \
     -I"$RAYLIB_DIR/src/external/glfw/include" \
     -Iinclude \
-    -DPLATFORM_WEB \
     "$RAYLIB_BUILD/libraylib.a" \
     $LDFLAGS
 
diff --git a/src/platform_web.c b/src/platform_web.c
index 32bd3f3..242bb78 100644
--- a/src/platform_web.c
+++ b/src/platform_web.c
@@ -10,6 +10,7 @@
 #include <string.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <errno.h>   /* ENOSYS */
 
 /* ── Helpers ─────────────────────────────────────────────────────────── */