diff --git a/include/lol/msg b/include/lol/msg
new file mode 100644
index 00000000..031d355b
--- /dev/null
+++ b/include/lol/msg
@@ -0,0 +1,18 @@
+//
+//  Lol Engine
+//
+//  Copyright © 2010—2020 Sam Hocevar <sam@hocevar.net>
+//
+//  Lol Engine is free software. It comes without any warranty, to
+//  the extent permitted by applicable law. You can redistribute it
+//  and/or modify it under the terms of the Do What the Fuck You Want
+//  to Public License, Version 2, as published by the WTFPL Task Force.
+//  See http://www.wtfpl.net/ for more details.
+//
+
+#pragma once
+
+#include "private/push_macros.h"
+#include "private/base/msg.h"
+#include "private/pop_macros.h"
+
diff --git a/include/lol/private/base/msg.h b/include/lol/private/base/msg.h
new file mode 100644
index 00000000..41e3f612
--- /dev/null
+++ b/include/lol/private/base/msg.h
@@ -0,0 +1,92 @@
+//
+//  Lol Engine
+//
+//  Copyright © 2010—2020 Sam Hocevar <sam@hocevar.net>
+//
+//  Lol Engine is free software. It comes without any warranty, to
+//  the extent permitted by applicable law. You can redistribute it
+//  and/or modify it under the terms of the Do What the Fuck You Want
+//  to Public License, Version 2, as published by the WTFPL Task Force.
+//  See http://www.wtfpl.net/ for more details.
+//
+
+#pragma once
+
+#if !_DEBUG
+#include "../base/env.h" // sys::getenv
+#endif
+
+#include <cstdio> // std::vfprintf
+
+namespace lol
+{
+
+struct msg
+{
+    template<typename... T>
+    static inline void debug(char const *fmt, T... args)
+    {
+        helper(message_type::debug, fmt, args...);
+    }
+
+    template<typename... T>
+    static inline void info(char const *fmt, T... args)
+    {
+        helper(message_type::info, fmt, args...);
+    }
+
+    template<typename... T>
+    static inline void warn(char const *fmt, T... args)
+    {
+        helper(message_type::warn, fmt, args...);
+    }
+
+    template<typename... T>
+    static inline void error(char const *fmt, T... args)
+    {
+        helper(message_type::error, fmt, args...);
+    }
+
+private:
+    msg() = delete;
+
+    enum class message_type
+    {
+        debug,
+        info,
+        warn,
+        error,
+    };
+
+    static void helper(message_type type, char const *fmt, ...)
+    {
+        // Unless this is a debug build, ignore debug messages unless
+        // the LOL_DEBUG environment variable is set.
+#if !_DEBUG
+        if (type == message_type::debug)
+        {
+            static bool const disable_debug = sys::getenv("LOL_DEBUG").size() > 0;
+            if (disable_debug)
+                return;
+        }
+#endif
+
+        static char const * const prefix[] =
+        {
+            "DEBUG",
+            "INFO",
+            "WARN",
+            "ERROR",
+        };
+
+        fprintf(stdout, "%s: ", prefix[int(type)]);
+        va_list ap;
+        va_start(ap, fmt);
+        vfprintf(stdout, fmt, ap);
+        va_end(ap);
+        fflush(stdout);
+    }
+};
+
+} // namespace lol
+