diff --git a/src/main.ts b/src/main.ts
index 77870ab..22e1b47 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -74,10 +74,10 @@ app.innerHTML = `
           <label class="control" for="retention-control">
             <span class="control__heading">
               <span>显影</span>
-              <output id="retention-value">14%</output>
+              <output id="retention-value">15%</output>
             </span>
             <span class="control__hint">留下多少原文词语</span>
-            <input id="retention-control" type="range" min="5" max="40" value="14" />
+            <input id="retention-control" type="range" min="0" max="100" value="15" />
           </label>
 
           <label class="control" for="volume-control">
@@ -86,7 +86,14 @@ app.innerHTML = `
               <output id="volume-value">100%</output>
             </span>
             <span class="control__hint">结果相对原文的总长度</span>
-            <input id="volume-control" type="range" min="85" max="115" value="100" />
+            <input
+              id="volume-control"
+              type="range"
+              min="10"
+              max="1000"
+              step="10"
+              value="100"
+            />
           </label>
 
           <label class="control" for="disorder-control">
diff --git a/src/mosaic.test.ts b/src/mosaic.test.ts
index dd0bb1a..82627a6 100644
--- a/src/mosaic.test.ts
+++ b/src/mosaic.test.ts
@@ -36,6 +36,14 @@ describe('selectKeywords', () => {
 
     expect(candidates.some((candidate) => candidate.selected)).toBe(true)
   })
+
+  it('显影 0% 不保留词语，100% 保留全部候选词', () => {
+    const hidden = selectKeywords(SOURCE, 0, 1)
+    const revealed = selectKeywords(SOURCE, 100, 1)
+
+    expect(hidden.some((candidate) => candidate.selected)).toBe(false)
+    expect(revealed.every((candidate) => candidate.selected)).toBe(true)
+  })
 })
 
 describe('generateMosaic', () => {
@@ -74,6 +82,22 @@ describe('generateMosaic', () => {
     expect(ratio).toBeLessThanOrEqual(1.03)
   })
 
+  it('支持将体量压缩到 10% 或膨胀到 1000%', () => {
+    const compressed = generateMosaic(SOURCE, [], {
+      volume: 10,
+      disorder: 0,
+      seed: 42,
+    })
+    const expanded = generateMosaic(SOURCE, [], {
+      volume: 1000,
+      disorder: 0,
+      seed: 42,
+    })
+
+    expect(compressed.outputLength).toBe(Math.round(compressed.inputLength * 0.1))
+    expect(expanded.outputLength).toBe(expanded.inputLength * 10)
+  })
+
   it('相同种子可复现，不同种子会重新侵蚀', () => {
     const candidates = selectKeywords(SOURCE, 14, 1)
     const first = generateMosaic(SOURCE, candidates, {
diff --git a/src/mosaic.ts b/src/mosaic.ts
index 113490e..dcce973 100644
--- a/src/mosaic.ts
+++ b/src/mosaic.ts
@@ -345,13 +345,13 @@ export function selectKeywords(
     return candidates
   }
 
-  const desiredCount = Math.min(
-    candidates.length,
-    Math.max(
-      candidates.length >= 4 ? 2 : 1,
-      Math.round(candidates.length * (retention / 100)),
-    ),
-  )
+  const desiredCount =
+    retention <= 0
+      ? 0
+      : Math.min(
+          candidates.length,
+          Math.max(1, Math.ceil(candidates.length * (retention / 100))),
+        )
   const ranked = [...candidates].sort(
     (left, right) => right.score - left.score || left.start - right.start,
   )