diff --git a/grammar.js b/grammar.js
index 2ea0227..9caabde 100644
--- a/grammar.js
+++ b/grammar.js
@@ -2,7 +2,7 @@ const PREC = {
   COMMENT: -2,
   EOL: -1,
   TEXT_BLOCK_CONTENT: -1,
-  UNQUOTED_STRING: 0,
+  UNQUOTED_STRING: -1,
   CONTAINER: 2,
   CONNECTION: 2,
   SHAPE: 3,
@@ -266,7 +266,8 @@ module.exports = grammar({
 
     label: ($) => choice($.string, $._unquoted_string),
 
-    attr_value: ($) => seq(choice($.string, $._unquoted_string)),
+    attr_value: ($) =>
+      seq(choice($.boolean, $.integer, $.float, $.string, $._unquoted_string)),
 
     // --------------------------------------------
 
@@ -288,6 +289,12 @@ module.exports = grammar({
         seq("`", repeat(token.immediate(/[^`\n]+/)), "`")
       ),
 
+    boolean: ($) => choice("true", "false"),
+
+    integer: ($) => /[0-9]+/,
+
+    float: ($) => /[0-9]+\.[0-9]+/,
+
     line_comment: ($) => token(prec(PREC.COMMENT, seq("#", /.*/))),
 
     _eol: ($) => token(prec(PREC.EOL, "\n")),
diff --git a/src/grammar.json b/src/grammar.json
index e89c666..7854d60 100644
--- a/src/grammar.json
+++ b/src/grammar.json
@@ -1115,6 +1115,18 @@
         {
           "type": "CHOICE",
           "members": [
+            {
+              "type": "SYMBOL",
+              "name": "boolean"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "integer"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "float"
+            },
             {
               "type": "SYMBOL",
               "name": "string"
@@ -1182,7 +1194,7 @@
       "type": "TOKEN",
       "content": {
         "type": "PREC",
-        "value": 0,
+        "value": -1,
         "content": {
           "type": "PATTERN",
           "value": "[^'\"`|\\n\\s;{}]([^\\n;{}]*[^\\n\\s;{}])?"
@@ -1263,6 +1275,27 @@
         }
       ]
     },
+    "boolean": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "true"
+        },
+        {
+          "type": "STRING",
+          "value": "false"
+        }
+      ]
+    },
+    "integer": {
+      "type": "PATTERN",
+      "value": "[0-9]+"
+    },
+    "float": {
+      "type": "PATTERN",
+      "value": "[0-9]+\\.[0-9]+"
+    },
     "line_comment": {
       "type": "TOKEN",
       "content": {
diff --git a/src/node-types.json b/src/node-types.json
index 4ec46b8..1512154 100644
--- a/src/node-types.json
+++ b/src/node-types.json
@@ -22,6 +22,18 @@
       "multiple": false,
       "required": false,
       "types": [
+        {
+          "type": "boolean",
+          "named": true
+        },
+        {
+          "type": "float",
+          "named": true
+        },
+        {
+          "type": "integer",
+          "named": true
+        },
         {
           "type": "string",
           "named": true
@@ -91,6 +103,11 @@
       ]
     }
   },
+  {
+    "type": "boolean",
+    "named": true,
+    "fields": {}
+  },
   {
     "type": "connection",
     "named": true,
@@ -349,10 +366,18 @@
     "type": "dot",
     "named": true
   },
+  {
+    "type": "false",
+    "named": false
+  },
   {
     "type": "fill",
     "named": false
   },
+  {
+    "type": "float",
+    "named": true
+  },
   {
     "type": "font-color",
     "named": false
@@ -365,6 +390,10 @@
     "type": "icon",
     "named": false
   },
+  {
+    "type": "integer",
+    "named": true
+  },
   {
     "type": "label",
     "named": false
@@ -421,6 +450,10 @@
     "type": "target-arrowhead",
     "named": false
   },
+  {
+    "type": "true",
+    "named": false
+  },
   {
     "type": "width",
     "named": false
diff --git a/src/parser.c b/src/parser.c
index 09532e9..81824c5 100644
Binary files a/src/parser.c and b/src/parser.c differ
diff --git a/test/corpus/attributes.txt b/test/corpus/attributes.txt
index 31b3b60..e6f46f5 100644
--- a/test/corpus/attributes.txt
+++ b/test/corpus/attributes.txt
@@ -4,17 +4,17 @@ Root attribute
 direction: value
 
 shape: oval
-label: ten
+label: 'one two'
 constraint: utehu
 icon: ./test.svg
-opacity: 1
+opacity: 0.5
 fill: red
 stroke: red
 stroke-width: 5
 stroke-dash: 4
 border-radius: 1
 font-color: red
-shadow: true
+shadow: false
 multiple: true
 animated: true
 link: https://to
@@ -26,19 +26,19 @@ near: abc
   (attribute (attr_key) (attr_value))
 
   (attribute (attr_key (reserved)) (attr_value))
+  (attribute (attr_key (reserved)) (attr_value (string)))
   (attribute (attr_key (reserved)) (attr_value))
   (attribute (attr_key (reserved)) (attr_value))
+  (attribute (attr_key (reserved)) (attr_value (float)))
   (attribute (attr_key (reserved)) (attr_value))
   (attribute (attr_key (reserved)) (attr_value))
+  (attribute (attr_key (reserved)) (attr_value (integer)))
+  (attribute (attr_key (reserved)) (attr_value (integer)))
+  (attribute (attr_key (reserved)) (attr_value (integer)))
   (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
-  (attribute (attr_key (reserved)) (attr_value))
+  (attribute (attr_key (reserved)) (attr_value (boolean)))
+  (attribute (attr_key (reserved)) (attr_value (boolean)))
+  (attribute (attr_key (reserved)) (attr_value (boolean)))
   (attribute (attr_key (reserved)) (attr_value))
   (attribute (attr_key (reserved)) (attr_value))
 )
@@ -46,14 +46,14 @@ near: abc
 ================================================================================
 Style attribute
 ================================================================================
-foo.style.opacity: 5
+foo.style.opacity: 0.5
 foo.style.fill: red
 foo.style.stroke: red
 foo.style.stroke-width: 5
 foo.style.stroke-dash: 4
 foo.style.border-radius: 1
 foo.style.font-color: red
-foo.style.shadow: true
+foo.style.shadow: false
 foo.style.multiple: true
 foo.style.animated: true
 foo.style.link: https://to
@@ -61,16 +61,16 @@ foo.style.link: https://to
 --------------------------------------------------------------------------------
 
 (source_file
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (float)))))
   (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
   (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer)))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer)))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer)))))
   (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
-  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean)))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean)))))
+  (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean)))))
   (shape (shape_key) (dot) (attribute (attr_key) (dot) (attribute (attr_key) (attr_value))))
 )
 
@@ -78,14 +78,14 @@ foo.style.link: https://to
 Block style attributes
 ================================================================================
 foo.style: {
-  opacity: 5
+  opacity: 0.5
   fill: red
   stroke: red
   stroke-width: 5
   stroke-dash: 4
   border-radius: 1
   font-color: red
-  shadow: true
+  shadow: false
   multiple: true
   animated: true
   link: https://to
@@ -99,16 +99,16 @@ foo.style: {
     (attribute
       (attr_key)
       (block
+        (attribute (attr_key) (attr_value (float)))
         (attribute (attr_key) (attr_value))
         (attribute (attr_key) (attr_value))
+        (attribute (attr_key) (attr_value (integer)))
+        (attribute (attr_key) (attr_value (integer)))
+        (attribute (attr_key) (attr_value (integer)))
         (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
-        (attribute (attr_key) (attr_value))
+        (attribute (attr_key) (attr_value (boolean)))
+        (attribute (attr_key) (attr_value (boolean)))
+        (attribute (attr_key) (attr_value (boolean)))
         (attribute (attr_key) (attr_value))
       )
     )
@@ -120,7 +120,7 @@ Container attributes
 ================================================================================
 foo: {
   shape: oval
-  label: Baz
+  label: 'Baz'
   constraint: primary-key
   icon: pathto
   width: 100
@@ -134,11 +134,11 @@ foo: {
     (container_key)
     (block
       (attribute (attr_key) (attr_value))
+      (attribute (attr_key) (attr_value (string)))
       (attribute (attr_key) (attr_value))
       (attribute (attr_key) (attr_value))
-      (attribute (attr_key) (attr_value))
-      (attribute (attr_key) (attr_value))
-      (attribute (attr_key) (attr_value))
+      (attribute (attr_key) (attr_value (integer)))
+      (attribute (attr_key) (attr_value (integer)))
     )
   )
 )
@@ -147,7 +147,7 @@ foo: {
 Container style attributes
 ================================================================================
 foo: {
-  style.opacity: 5
+  style.opacity: 0.5
   style.fill: red
   style.stroke: red
   style.stroke-width: 5
@@ -166,16 +166,16 @@ foo: {
   (container
     (container_key)
     (block
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (float))))
       (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
       (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer))))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer))))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (integer))))
       (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
-      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean))))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean))))
+      (attribute (attr_key) (dot) (attribute (attr_key) (attr_value (boolean))))
       (attribute (attr_key) (dot) (attribute (attr_key) (attr_value)))
     )
   )
@@ -186,7 +186,7 @@ Block style attributes inside a container
 ================================================================================
 foo: {
   style: {
-    opacity: 5
+    opacity: 0.5
     fill: red
     stroke: red
     stroke-width: 5
@@ -209,16 +209,16 @@ foo: {
       (attribute
         (attr_key)
         (block
+          (attribute (attr_key) (attr_value (float)))
           (attribute (attr_key) (attr_value))
           (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (integer)))
+          (attribute (attr_key) (attr_value (integer)))
+          (attribute (attr_key) (attr_value (integer)))
           (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (boolean)))
+          (attribute (attr_key) (attr_value (boolean)))
+          (attribute (attr_key) (attr_value (boolean)))
           (attribute (attr_key) (attr_value))
         )
       )
@@ -231,14 +231,14 @@ Block style attributes inside a connection
 ================================================================================
 foo -> bar: {
   style: {
-    opacity: 5
+    opacity: 0.5
     fill: red
     stroke: red
     stroke-width: 5
     stroke-dash: 4
     border-radius: 1
     font-color: red
-    shadow: true
+    shadow: false
     multiple: true
     animated: true
     link: https://to
@@ -256,16 +256,16 @@ foo -> bar: {
       (attribute
         (attr_key)
         (block
+          (attribute (attr_key) (attr_value (float)))
           (attribute (attr_key) (attr_value))
           (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (integer)))
+          (attribute (attr_key) (attr_value (integer)))
+          (attribute (attr_key) (attr_value (integer)))
           (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (boolean)))
+          (attribute (attr_key) (attr_value (boolean)))
+          (attribute (attr_key) (attr_value (boolean)))
           (attribute (attr_key) (attr_value))
         )
       )
@@ -307,14 +307,14 @@ Block style attributes inside a connection arrowhead
 foo -> bar: {
   target-arrowhead: {
     style: {
-      opacity: 5
+      opacity: 0.5
       fill: red
       stroke: red
       stroke-width: 5
       stroke-dash: 4
       border-radius: 1
       font-color: red
-      shadow: true
+      shadow: false
       multiple: true
       animated: true
       link: https://to
@@ -336,16 +336,16 @@ foo -> bar: {
           (attribute
             (attr_key)
             (block
+              (attribute (attr_key) (attr_value (float)))
               (attribute (attr_key) (attr_value))
               (attribute (attr_key) (attr_value))
+              (attribute (attr_key) (attr_value (integer)))
+              (attribute (attr_key) (attr_value (integer)))
+              (attribute (attr_key) (attr_value (integer)))
               (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
-              (attribute (attr_key) (attr_value))
+              (attribute (attr_key) (attr_value (boolean)))
+              (attribute (attr_key) (attr_value (boolean)))
+              (attribute (attr_key) (attr_value (boolean)))
               (attribute (attr_key) (attr_value))
             )
           )
@@ -361,7 +361,7 @@ Container attributes inside a connection arrowhead
 foo -> bar: {
   target-arrowhead: {
     shape: oval
-    label: Baz
+    label: 'Baz'
     constraint: primary-key
     icon: pathto
     width: 100
@@ -381,11 +381,11 @@ foo -> bar: {
         (attr_key)
         (block
           (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (string)))
           (attribute (attr_key) (attr_value))
           (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
-          (attribute (attr_key) (attr_value))
+          (attribute (attr_key) (attr_value (integer)))
+          (attribute (attr_key) (attr_value (integer)))
         )
       )
     )