diff --git a/server/public/admin.html b/server/public/admin.html
index 452a4fd..b782f82 100644
--- a/server/public/admin.html
+++ b/server/public/admin.html
@@ -55,7 +55,7 @@
       max-width: none; cursor: grab;
     }
     .crop-mask {
-      position: absolute; inset: 0; pointer-events: none;
+      position: absolute; left: 0; top: 0; pointer-events: none;
       box-shadow: 0 0 0 9999px rgba(0, 0, 0, 0.45);
       border: 2px solid #fff; border-radius: 4px;
     }
@@ -167,11 +167,8 @@
       lastY: 0
     }
 
-    function layoutCrop() {
+    function maskSize() {
       const stage = document.getElementById('cropStage')
-      const img = document.getElementById('cropImage')
-      const mask = document.getElementById('cropMask')
-      if (!stage || !img.naturalWidth) return
       const sw = stage.clientWidth
       const sh = stage.clientHeight
       let maskW = sw - 32
@@ -180,10 +177,31 @@
         maskH = sh - 32
         maskW = maskH * COVER_RATIO
       }
-      mask.style.width = `${maskW}px`
-      mask.style.height = `${maskH}px`
-      mask.style.left = `${(sw - maskW) / 2}px`
-      mask.style.top = `${(sh - maskH) / 2}px`
+      return {
+        maskW: maskW,
+        maskH: maskH,
+        maskLeft: (sw - maskW) / 2,
+        maskTop: (sh - maskH) / 2
+      }
+    }
+
+    function minCropScale() {
+      const size = maskSize()
+      return Math.max(size.maskW / cropState.naturalW, size.maskH / cropState.naturalH)
+    }
+
+    function layoutCrop() {
+      const stage = document.getElementById('cropStage')
+      const img = document.getElementById('cropImage')
+      const mask = document.getElementById('cropMask')
+      if (!stage || !img.naturalWidth || !cropState.naturalW) return
+      const size = maskSize()
+      mask.style.right = 'auto'
+      mask.style.bottom = 'auto'
+      mask.style.width = `${size.maskW}px`
+      mask.style.height = `${size.maskH}px`
+      mask.style.left = `${size.maskLeft}px`
+      mask.style.top = `${size.maskTop}px`
 
       img.style.width = `${cropState.naturalW * cropState.scale}px`
       img.style.height = `${cropState.naturalH * cropState.scale}px`
@@ -192,15 +210,28 @@
 
     function fitCropImage() {
       const stage = document.getElementById('cropStage')
-      const maskW = Math.min(stage.clientWidth - 32, (stage.clientHeight - 32) * COVER_RATIO)
-      const maskH = maskW / COVER_RATIO
-      const scale = Math.max(maskW / cropState.naturalW, maskH / cropState.naturalH)
+      const scale = minCropScale()
       cropState.scale = scale
       cropState.x = (stage.clientWidth - cropState.naturalW * scale) / 2
       cropState.y = (stage.clientHeight - cropState.naturalH * scale) / 2
       layoutCrop()
     }
 
+    function zoomCrop(factor) {
+      if (!cropState.naturalW) return
+      const size = maskSize()
+      const cx = size.maskLeft + size.maskW / 2
+      const cy = size.maskTop + size.maskH / 2
+      const before = cropState.scale
+      const next = Math.min(Math.max(before * factor, minCropScale()), minCropScale() * 8)
+      if (Math.abs(next - before) < 0.0001) return
+      // Keep the point under the crop center stable while zooming.
+      cropState.x = cx - ((cx - cropState.x) / before) * next
+      cropState.y = cy - ((cy - cropState.y) / before) * next
+      cropState.scale = next
+      layoutCrop()
+    }
+
     function openCoverCrop(file, targetInput, hint) {
       const modal = document.getElementById('cropModal')
       const img = document.getElementById('cropImage')
@@ -270,14 +301,19 @@
       })
       stage.addEventListener('pointerup', () => { cropState.dragging = false })
       stage.addEventListener('pointercancel', () => { cropState.dragging = false })
-      document.getElementById('cropZoomIn').onclick = () => {
-        cropState.scale *= 1.12
-        layoutCrop()
+      document.getElementById('cropZoomIn').onclick = (event) => {
+        event.preventDefault()
+        zoomCrop(1.15)
       }
-      document.getElementById('cropZoomOut').onclick = () => {
-        cropState.scale /= 1.12
-        layoutCrop()
+      document.getElementById('cropZoomOut').onclick = (event) => {
+        event.preventDefault()
+        zoomCrop(1 / 1.15)
       }
+      stage.addEventListener('wheel', (event) => {
+        if (!document.getElementById('cropModal').classList.contains('on')) return
+        event.preventDefault()
+        zoomCrop(event.deltaY > 0 ? 1 / 1.08 : 1.08)
+      }, { passive: false })
       document.getElementById('cropCancel').onclick = closeCoverCrop
       document.getElementById('cropConfirm').onclick = async () => {
         const hint = cropState.hint