diff --git a/build/common_compiler_flags.py b/build/common_compiler_flags.py
index bbf54ce..a9e0822 100644
--- a/build/common_compiler_flags.py
+++ b/build/common_compiler_flags.py
@@ -54,6 +54,15 @@ def generate(env):
             env.Append(CCFLAGS=["-fvisibility=hidden"])
             env.Append(LINKFLAGS=["-fvisibility=hidden"])
 
+    if env["optimize"] == "speed":
+        env.Append(CPPDEFINES=["OPT_SPEED_ENABLED"])
+    elif env["optimize"] == "speed_trace":
+        env.Append(CPPDEFINES=["OPT_SPEED_TRACE_ENABLED"])
+    elif env["optimize"] == "size":
+        env.Append(CPPDEFINES=["OPT_SIZE_ENABLED"])
+    elif env["optimize"] == "debug":
+        env.Append(CPPDEFINES=["OPT_DEBUG_ENABLED"])
+
     # Set optimize and debug_symbols flags.
     # "custom" means do nothing and let users set their own optimization flags.
     if env.get("is_msvc", False):
diff --git a/tools/targets.py b/tools/targets.py
index 7786607..34044e9 100644
--- a/tools/targets.py
+++ b/tools/targets.py
@@ -43,9 +43,10 @@ def options(opts):
     opts.Add(
         EnumVariable(
             "optimize",
-            "The desired optimization flags",
-            "speed_trace",
-            ("none", "custom", "debug", "speed", "speed_trace", "size"),
+            "Optimization level (by default inferred from 'target' and 'dev_build')",
+            "auto",
+            ["auto", "none", "custom", "debug", "speed", "speed_trace", "size"],
+            ignorecase=2,
         )
     )
     opts.Add(
@@ -79,14 +80,15 @@ def generate(env):
     env.dev_build = env["dev_build"]
     env.debug_features = env["target"] in ["editor", "template_debug"]
 
-    if env.dev_build:
-        opt_level = "none"
-    elif env.debug_features:
-        opt_level = "speed_trace"
-    else:  # Release
-        opt_level = "speed"
+    if env["optimize"] == "auto":
+        if env.dev_build:
+            opt_level = "none"
+        elif env.debug_features:
+            opt_level = "speed_trace"
+        else:  # Release
+            opt_level = "speed"
+        env["optimize"] = ARGUMENTS.get("optimize", opt_level)
 
-    env["optimize"] = ARGUMENTS.get("optimize", opt_level)
     env["debug_symbols"] = get_cmdline_bool("debug_symbols", env.dev_build)
 
     if env.use_hot_reload: