diff --git a/projects/code-span/src/view/iter.rs b/projects/code-span/src/view/iter.rs
index 4e2bb5e..5be1bff 100644
--- a/projects/code-span/src/view/iter.rs
+++ b/projects/code-span/src/view/iter.rs
@@ -1,6 +1,6 @@
-use std::{collections::BTreeSet, ops::Range};
+use std::ops::Range;
 
-use crate::view::{CodeRender, CodeView, InnerSpan};
+use crate::view::{CodeRender, CodeView, IntervalRepr};
 
 /// # Arguments
 ///
@@ -17,7 +17,7 @@ use crate::view::{CodeRender, CodeView, InnerSpan};
 #[derive(Debug)]
 pub struct CodeRendered<'r, 'i, 's> {
     text: &'i str,
-    iter: std::collections::btree_map::Iter<'r, usize, InnerSpan<'s>>,
+    iter: std::collections::btree_map::Iter<'r, usize, IntervalRepr<'s>>,
 }
 
 impl<'r, 'i, 's> IntoIterator for &'r CodeRender<'i, 's> {
@@ -25,7 +25,7 @@ impl<'r, 'i, 's> IntoIterator for &'r CodeRender<'i, 's> {
     type IntoIter = CodeRendered<'r, 'i, 's>;
 
     fn into_iter(self) -> Self::IntoIter {
-        CodeRendered { text: self.text, iter: self.interval.iter() }
+        CodeRendered { text: self.text, iter: self.intervals.iter() }
     }
 }
 
diff --git a/projects/code-span/src/view/mod.rs b/projects/code-span/src/view/mod.rs
index 4bc83bf..d435ca1 100644
--- a/projects/code-span/src/view/mod.rs
+++ b/projects/code-span/src/view/mod.rs
@@ -11,62 +11,78 @@ pub struct CodeRender<'i, 's> {
     /// raw text
     text: &'i str,
     /// start -> (styles , end)
-    interval: BTreeMap<usize, InnerSpan<'s>>,
+    intervals: BTreeMap<usize, IntervalRepr<'s>>,
 }
 
 #[derive(Clone, Debug)]
-struct InnerSpan<'s> {
+struct IntervalRepr<'s> {
     styles: BTreeSet<&'s str>,
     end: usize,
 }
 
-#[derive(Copy, Clone, Debug)]
-pub struct CodeView<'r, 'i, 's> {
-    pub text: &'i str,
-    pub kind: &'r BTreeSet<&'s str>,
-}
-
 impl<'i, 's> CodeRender<'i, 's> {
     pub fn new(text: &'i str) -> Self {
         let mut interval = BTreeMap::new();
-        interval.insert(0, InnerSpan { styles: Default::default(), end: text.len() });
-        Self { text, interval }
+        interval.insert(0, IntervalRepr { styles: Default::default(), end: text.len() });
+        Self { text, intervals: interval }
     }
     pub fn get_span<'r>(&'r mut self, offset: usize) -> Option<CodeView<'r, 'i, 's>> {
-        let (start, span) = self.interval.range(offset..).next()?;
+        let (start, span) = self.intervals.range(offset..).next()?;
         let range = Range { start: *start, end: span.end };
         let text = self.text.get(range.clone())?;
         Some(CodeView { text, kind: &span.styles })
     }
     pub fn mark_span(&mut self, span: Range<usize>, style: &'s str) {
-        match self.interval.get(&span.start) {
+        match self.intervals.get(&span.start) {
             Some(_) => {
-                match self.interval.get(&span.end) {
-                    // easy case, no need modifier old interval
-                    Some(_) => self.interval.range_mut(span).for_each(|(_, inner)| {
-                        inner.styles.insert(style);
-                    }),
+                match self.intervals.get(&span.end) {
+                    // simple case, no need change old interval
+                    Some(_) => self.mark_span_unchecked(span, style),
+                    // remark end position
                     None => {
-                        todo!()
+                        let (_, last_span) = self.intervals.range(span.end..).next().unwrap();
+                        let new_end = last_span.end;
+                        let new_styles = last_span.styles.clone();
+                        self.intervals.remove(&span.end);
+                        self.intervals.entry(span.end).or_insert(IntervalRepr { styles: new_styles, end: new_end });
+                        self.mark_span_unchecked(span, style)
                     }
                 }
             }
             None => {
-                // 修改前一个区间的结束位置
-                self.interval.range_mut(..span.start).next_back().map(|(_, v)| {
-                    v.end = span.start;
-                });
-                todo!()
+                // truncate the previous span
+                let prev_span = self.intervals.range_mut(..span.start).next_back();
+                if let Some((_, prev_inner)) = prev_span {
+                    prev_inner.end = span.start;
+                }
+                // insert start position
+                let (_, next_span) = self.intervals.range(span.start..).next().unwrap();
+                let new_end = next_span.end;
+                let new_styles = next_span.styles.clone();
+                self.intervals.remove(&span.start);
+                self.intervals.entry(span.start).or_insert(IntervalRepr { styles: new_styles, end: new_end });
+                self.mark_span_unchecked(span, style)
             }
         }
     }
+    fn mark_span_unchecked(&mut self, span: Range<usize>, style: &'s str) {
+        for (_, inner) in self.intervals.range_mut(span) {
+            inner.styles.insert(style);
+        }
+    }
 }
 
 #[test]
 fn main() {
     let mut code_render = CodeRender::new("public class Main {}");
-    code_render.mark_span(0..17, "class");
-    code_render.mark_span(0..3, "keyword");
+    code_render.mark_span(0..6, "keyword");
     code_render.mark_span(7..12, "keyword");
+    code_render.mark_span(13..17, "class");
     println!("{:#?}", code_render);
 }
+
+#[derive(Copy, Clone, Debug)]
+pub struct CodeView<'r, 'i, 's> {
+    pub text: &'i str,
+    pub kind: &'r BTreeSet<&'s str>,
+}