diff --git a/examples/random.cal b/examples/random.cal
new file mode 100644
index 0000000..856c690
--- /dev/null
+++ b/examples/random.cal
@@ -0,0 +1,11 @@
+include "cores/select.cal"
+include "std/io.cal"
+include "std/random.cal"
+
+let cell i
+0 i !
+
+while i @ 10 < do
+	rand printdec new_line
+	i @ 1 + i !
+end
diff --git a/examples/time.cal b/examples/time.cal
new file mode 100644
index 0000000..d37cc31
--- /dev/null
+++ b/examples/time.cal
@@ -0,0 +1,6 @@
+include "cores/select.cal"
+include "std/io.cal"
+
+requires Time
+
+get_epoch_time printdec new_line
diff --git a/micro_callisto.yaml b/micro_callisto.yaml
new file mode 100644
index 0000000..c610a11
--- /dev/null
+++ b/micro_callisto.yaml
@@ -0,0 +1,39 @@
+filetype: callisto
+
+detect:
+    filename: "\\.(cal)$"
+
+rules:
+    - statement: "\\b(func|end|begin|asm|include|inline|if|then|elseif|else|while|do)\\b"
+    - statement: "\\b(let|feature|implements|requires|struct|version|return|const)\\b"
+    - type:      "\\b(addr|void|u8|i8|u16|i16|u32|i32|u64|i64|size|usize|cell|array)\\b"
+    - identifier: "\\$\\{?[0-9A-Za-z._!@#$*?-]+\\}?"
+    - identifier: "\\$\\{?[0-9A-Za-z._!@#$*?-]+\\}?"
+    - identifier: "\\*\\{?[0-9A-Za-z._!@#$*?-]+\\}?"
+    - identifier: "\\!\\{?[0-9A-Za-z._!@#$*?-]+\\}?"
+    
+    - constant.string:
+        start: "\""
+        end: "\""
+        skip: "\\\\."
+        rules:
+            - constant.specialChar: "\\\\([\"'abfnrtv\\\\]|[0-3]?[0-7]{1,2}|x[0-9A-Fa-f]{1,2}|u[0-9A-Fa-f]{4}|U[0-9A-Fa-f]{8})"
+
+    - constant.string:
+        start: "'"
+        end: "'"
+        skip: "\\\\."
+        rules:
+            - constant.specialChar: "\\\\([\"'abfnrtv\\\\]|[0-3]?[0-7]{1,2}|x[0-9A-Fa-f]{1,2}|u[0-9A-Fa-f]{4}|U[0-9A-Fa-f]{8})"
+
+    - constant.number: "\\b([0-9.]*)\\b"
+    - constant.number: "\\b(0b[0-1.]*)\\b"
+    - constant.number: "\\b(0x[0-9A-Fa-f.]*)\\b"
+    - constant.number: "\\b(0o[0-7.]*)\\b"
+    - constant.bool: "\\b(true|false)\\b"
+    
+    - comment:
+        start: "#"
+        end: "$"
+        rules:
+            - todo: "(TODO|XXX|FIXME):?"
diff --git a/source/backends/linux86.d b/source/backends/linux86.d
index 7d37906..4faa00e 100644
--- a/source/backends/linux86.d
+++ b/source/backends/linux86.d
@@ -92,7 +92,7 @@ class BackendLinux86 : CompilerBackend {
 		NewConst("Array.sizeof",     8 * 3);
 	}
 
-	void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
+	override void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
 		consts[name] = Constant(new IntegerNode(error, value));
 	}
 
@@ -167,7 +167,7 @@ class BackendLinux86 : CompilerBackend {
 		output ~= "section .bss\n";
 
 		foreach (name, var ; globals) {
-			output ~= format("__global_%s: resb %d\n", name, var.Size());
+			output ~= format("__global_%s: resb %d\n", name.Sanitise(), var.Size());
 		}
 
 		foreach (i, ref array ; arrays) {
@@ -522,6 +522,10 @@ class BackendLinux86 : CompilerBackend {
 	}
 
 	override void CompileConst(ConstNode node) {
+		if (node.name in consts) {
+			Error(node.error, "Constant '%s' already defined", node.name);
+		}
+		
 		NewConst(node.name, node.value);
 	}
 }
diff --git a/source/backends/rm86.d b/source/backends/rm86.d
index 80cb45c..8f4206c 100644
--- a/source/backends/rm86.d
+++ b/source/backends/rm86.d
@@ -87,7 +87,7 @@ class BackendRM86 : CompilerBackend {
 		NewConst("Array.sizeof",     2 * 3);
 	}
 
-	void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
+	override void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
 		consts[name] = Constant(new IntegerNode(error, value));
 	}
 
@@ -485,6 +485,10 @@ class BackendRM86 : CompilerBackend {
 	}
 
 	override void CompileConst(ConstNode node) {
+		if (node.name in consts) {
+			Error(node.error, "Constant '%s' already defined", node.name);
+		}
+		
 		NewConst(node.name, node.value);
 	}
 }
diff --git a/source/backends/y16.d b/source/backends/y16.d
index 9764ece..30b6926 100644
--- a/source/backends/y16.d
+++ b/source/backends/y16.d
@@ -81,7 +81,7 @@ class BackendY16 : CompilerBackend {
 		NewConst("Array.elements",   4);
 	}
 
-	void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
+	override void NewConst(string name, long value, ErrorInfo error = ErrorInfo.init) {
 		consts[name] = Constant(new IntegerNode(error, value));
 	}
 	
@@ -324,6 +324,10 @@ class BackendY16 : CompilerBackend {
 	}
 
 	override void CompileConst(ConstNode node) {
+		if (node.name in consts) {
+			Error(node.error, "Constant '%s' already defined", node.name);
+		}
+		
 		NewConst(node.name, node.value);
 	}
 }
diff --git a/source/compiler.d b/source/compiler.d
index ed028fd..d133970 100644
--- a/source/compiler.d
+++ b/source/compiler.d
@@ -19,6 +19,7 @@ class CompilerBackend {
 
 	abstract string[] GetVersions();
 	abstract string[] FinalCommands();
+	abstract void NewConst(string name, long value, ErrorInfo error);
 
 	abstract void Init();
 	abstract void End();
diff --git a/std b/std
index 70302bb..b43465c 160000
--- a/std
+++ b/std
@@ -1 +1 @@
-Subproject commit 70302bbc679278752b3bc88ee6fcf37b94390d10
+Subproject commit b43465cb1b4cd656df54dd5bc47e99049eca5ec4