diff --git a/apps/web/src/admin/api.ts b/apps/web/src/admin/api.ts
index 99cd557..862076a 100644
--- a/apps/web/src/admin/api.ts
+++ b/apps/web/src/admin/api.ts
@@ -9,7 +9,7 @@ import type {
   AdminAiReportList,
   StuckProblem,
   StuckProblemDetail,
-  YearlyOverview,
+  GradeTrendProblem,
   LearnBoard,
   LearnExerciseProgressList,
   LearnExerciseAttempt,
@@ -624,8 +624,8 @@ export function getLearnExerciseAttempts(exerciseId: number, params: { className
   })
 }
 
-export function getYearlyOverview() {
-  return api.get<YearlyOverview>("admin/problem-analytics/yearly")
+export function getGradeTrend() {
+  return api.get<GradeTrendProblem[]>("admin/problem-analytics/grades")
 }
 
 // AI 学习分析报告
diff --git a/apps/web/src/admin/problem/Trend.vue b/apps/web/src/admin/problem/Trend.vue
index 9245af0..aace936 100644
--- a/apps/web/src/admin/problem/Trend.vue
+++ b/apps/web/src/admin/problem/Trend.vue
@@ -1,126 +1,140 @@
 <script setup lang="ts">
-import type { YearlyOverview, YearlySummary } from "utils/types"
-import { getYearlyOverview } from "admin/api"
-import { parseTime } from "utils/functions"
+import { useRouteQuery } from "@vueuse/router"
+import type { GradeTrendProblem } from "utils/types"
+import { getGradeTrend } from "admin/api"
 import "oj/learn/learn.css"
 
 /**
- * 历年概况（原「年度趋势」，设计稿「卡点与趋势」页的定稿 TrendFinal）：一个学年一列。
+ * 年度趋势（设计稿「卡点与趋势」页的 TrendB）：选一届，和往届（或另一届）在两边都做过的题上
+ * 逐题比「一次就对」，比往届差的排前面。
  *
- * 学年从 9 月 1 日算起（原来按自然年切，一个学年被切成两半）。进行中的学年只有几个月，
- * 拿它和整年比没有意义，所以旁边并排一列「去年同期」。单道题的历年变化挪进了卡点分析的右栏。
- * 口径（人 × 题、一次就对、做对之前交了几次）见后端 routes/admin/analytics.ts。
+ * 按届（班号前两位）比而不是按自然年：一个学年里同时有两三届在做题，按年切会把它们搅在一起。
+ * 往届是把更早几届的人合在一起算（人多的届分量大），不是几个百分比再平均。
+ * 比输赢按显示出来的整数百分比，差 2 个点以内算差不多。
  */
-const data = ref<YearlyOverview | null>(null)
+const router = useRouter()
+
+/** 每边至少这么多人做过，这道题才拿来比 */
+const MIN_USERS = 20
+const SAME = 2
+const PAST = "past"
+
+const problems = ref<GradeTrendProblem[]>([])
 const loading = ref(false)
+const grade = useRouteQuery<string>("grade", "", { mode: "replace" })
+const compare = useRouteQuery<string>("compare", PAST, { mode: "replace" })
 
-interface Column {
-  key: string
-  title: string
-  sub: string
-  kind: "full" | "current" | "last"
-  row: YearlySummary
+/** 有数据的届，新的在前 */
+const grades = computed(() =>
+  [...new Set(problems.value.flatMap((row) => row.grades.map((cell) => cell.grade)))].sort((a, b) =>
+    b.localeCompare(a),
+  ),
+)
+
+function side(row: GradeTrendProblem, pick: (g: string) => boolean) {
+  return row.grades
+    .filter((cell) => pick(cell.grade))
+    .reduce(
+      (sum, cell) => ({ users: sum.users + cell.users, firstTry: sum.firstTry + cell.firstTry }),
+      {
+        users: 0,
+        firstTry: 0,
+      },
+    )
 }
 
-function yearLabel(year: number) {
-  return `${String(year).slice(2)}–${String(year + 1).slice(2)}`
+function rate(part: number, whole: number) {
+  return whole ? Math.round((part / whole) * 100) : 0
 }
 
-/** `until` 是开区间的终点，显示成「到 X 月 X 日」得往前退一毫秒 */
-function untilText(until: string) {
-  return `到 ${parseTime(new Date(Date.parse(until) - 1), "M月D日")}`
-}
-
-const columns = computed<Column[]>(() => {
-  if (!data.value) return []
-  const years = data.value.years
-  const out: Column[] = years.map((row, index) => {
-    const current = index === years.length - 1
-    return {
-      key: String(row.year),
-      title: yearLabel(row.year),
-      sub: current ? untilText(row.until) : "",
-      kind: current ? "current" : "full",
-      row,
-    }
-  })
-  const last = data.value.lastYearToDate
-  if (last)
-    out.push({
-      key: "last",
-      title: "去年同期",
-      sub: `${yearLabel(last.year)} ${untilText(last.until)}`,
-      kind: "last",
-      row: last,
+function compareRows(current: string, other: string) {
+  const isOther = other === PAST ? (g: string) => g < current : (g: string) => g === other
+  return problems.value
+    .map((row) => {
+      const mine = side(row, (g) => g === current)
+      const theirs = side(row, isOther)
+      const now = rate(mine.firstTry, mine.users)
+      const before = rate(theirs.firstTry, theirs.users)
+      return { row, mine, theirs, now, before, delta: now - before }
     })
-  return out
+    .filter((item) => item.mine.users >= MIN_USERS && item.theirs.users >= MIN_USERS)
+}
+
+/** 没选就挑最新的一届里能和往届比上至少 5 道题的 */
+const selected = computed(() => {
+  if (grades.value.includes(grade.value)) return grade.value
+  return grades.value.find((g) => compareRows(g, PAST).length >= 5) ?? grades.value[0] ?? ""
 })
 
-function ratio(part: number, whole: number, digits = 0) {
-  return whole ? Number(((part / whole) * (digits ? 1 : 100)).toFixed(digits)) : 0
-}
+const pastGrades = computed(() => grades.value.filter((g) => g < selected.value))
+const pastLabel = computed(() => {
+  const list = pastGrades.value
+  if (!list.length) return "往届"
+  return list.length === 1 ? `往届（${list[0]} 级）` : `往届（${list.at(-1)}–${list[0]} 级）`
+})
+const otherLabel = computed(() =>
+  compare.value === PAST ? pastLabel.value : `${compare.value} 级`,
+)
+const shortOther = computed(() => (compare.value === PAST ? "往届" : `${compare.value} 级`))
 
-interface Line {
-  label: string
-  /** 给人看的 */
-  text: (row: YearlySummary) => string
-  /** 画小横条用的值，只给数量类的行 */
-  value?: (row: YearlySummary) => number
-}
+const gradeOptions = computed(() => grades.value.map((g) => ({ label: `${g} 级`, value: g })))
+const compareOptions = computed(() => [
+  { label: pastLabel.value, value: PAST },
+  ...grades.value.filter((g) => g !== selected.value).map((g) => ({ label: `${g} 级`, value: g })),
+])
 
-const LINES: Line[] = [
-  {
-    label: "在用的年级",
-    text: (row) => (row.grades.length ? row.grades.map((g) => `${g}`).join(" · ") + " 级" : "-"),
-  },
-  { label: "做题的学生", text: (row) => `${row.users} 人`, value: (row) => row.users },
-  {
-    label: "提交",
-    text: (row) => `${row.submissions.toLocaleString("en-US")} 次`,
-    value: (row) => row.submissions,
-  },
-  { label: "做过的题", text: (row) => `${row.problems} 道`, value: (row) => row.problems },
-  {
-    label: "人均做对",
-    text: (row) => `${ratio(row.solvedPairs, row.users, 1)} 道`,
-    value: (row) => ratio(row.solvedPairs, row.users, 1),
-  },
-  { label: "一次就对", text: (row) => `${ratio(row.firstTryPairs, row.startedPairs)}%` },
-  {
-    label: "做对平均交",
-    text: (row) => (row.solvedStarted ? `${ratio(row.solvedTries, row.solvedStarted, 1)} 次` : "-"),
-  },
-  { label: "C / C++ 提交", text: (row) => `${ratio(row.cSubmissions, row.submissions)}%` },
-]
+const rows = computed(() => (selected.value ? compareRows(selected.value, compare.value) : []))
+const worse = computed(() =>
+  rows.value.filter((item) => item.delta < -SAME).sort((a, b) => a.delta - b.delta),
+)
+const same = computed(() =>
+  rows.value.filter((item) => Math.abs(item.delta) <= SAME).sort((a, b) => a.delta - b.delta),
+)
+const better = computed(() =>
+  rows.value.filter((item) => item.delta > SAME).sort((a, b) => b.delta - a.delta),
+)
 
-/** 小横条只在完整学年之间比，进行中的和去年同期都只有几个月 */
-function barWidth(line: Line, column: Column) {
-  if (!line.value || column.kind !== "full") return null
-  const max = Math.max(
-    1,
-    ...columns.value.filter((c) => c.kind === "full").map((c) => line.value!(c.row)),
+const summary = computed(() => {
+  const total = rows.value.reduce(
+    (sum, item) => ({
+      mineUsers: sum.mineUsers + item.mine.users,
+      mineFirst: sum.mineFirst + item.mine.firstTry,
+      theirUsers: sum.theirUsers + item.theirs.users,
+      theirFirst: sum.theirFirst + item.theirs.firstTry,
+    }),
+    { mineUsers: 0, mineFirst: 0, theirUsers: 0, theirFirst: 0 },
   )
-  return `${(line.value(column.row) / max) * 100}%`
+  return {
+    now: rate(total.mineFirst, total.mineUsers),
+    before: rate(total.theirFirst, total.theirUsers),
+  }
+})
+
+const groups = computed(() =>
+  [
+    { key: "worse", label: `比${shortOther.value}差`, items: worse.value },
+    { key: "same", label: "差不多", items: same.value },
+    { key: "better", label: `比${shortOther.value}好`, items: better.value },
+  ].filter((group) => group.items.length),
+)
+
+function tone(delta: number) {
+  return delta < -SAME ? "worse" : delta > SAME ? "better" : "same"
 }
 
-function exportCsv() {
-  const quote = (text: string) => `"${text.replaceAll('"', '""')}"`
-  const head = ["", ...columns.value.map((c) => [c.title, c.sub].filter(Boolean).join(" "))]
-  const rows = LINES.map((line) => [line.label, ...columns.value.map((c) => line.text(c.row))])
-  const csv = [head, ...rows].map((row) => row.map(quote).join(",")).join("\r\n")
-  // 带 BOM，Excel 才按 UTF-8 打开，不然中文是乱码
-  const url = URL.createObjectURL(new Blob(["" + csv], { type: "text/csv;charset=utf-8" }))
-  const link = document.createElement("a")
-  link.href = url
-  link.download = "历年概况.csv"
-  link.click()
-  URL.revokeObjectURL(url)
+function problemHref(displayId: string) {
+  return router.resolve({ name: "problem", params: { problemID: displayId } }).href
+}
+
+function pickGrade(value: string) {
+  grade.value = value
+  if (compare.value === value) compare.value = PAST
 }
 
 onMounted(async () => {
   loading.value = true
   try {
-    data.value = await getYearlyOverview()
+    problems.value = await getGradeTrend()
   } finally {
     loading.value = false
   }
@@ -130,51 +144,126 @@ onMounted(async () => {
 <template>
   <div class="page">
     <div class="top">
-      <span class="title">历年概况</span>
+      <span class="title">年度趋势</span>
       <span class="grow" />
-      <n-button :disabled="!columns.length" @click="exportCsv">导出表格</n-button>
+      <span class="muted">比</span>
+      <n-select
+        :value="selected || null"
+        :options="gradeOptions"
+        style="width: 100px"
+        @update:value="pickGrade"
+      />
+      <span class="muted">和</span>
+      <n-select
+        :value="compare"
+        :options="compareOptions"
+        style="width: 170px"
+        @update:value="(value: string) => (compare = value)"
+      />
     </div>
+
     <n-spin :show="loading">
-      <section class="card">
-        <div class="scroll">
-          <table>
-            <thead>
-              <tr>
-                <th class="label muted">学年（9 月起）</th>
-                <th v-for="column in columns" :key="column.key" :class="column.kind">
-                  <div>{{ column.title }}</div>
-                  <div v-if="column.sub" class="sub">{{ column.sub }}</div>
-                </th>
-              </tr>
-            </thead>
-            <tbody>
-              <tr v-for="line in LINES" :key="line.label">
-                <td class="label">{{ line.label }}</td>
-                <td v-for="column in columns" :key="column.key" :class="column.kind" class="num">
-                  <div>{{ line.text(column.row) }}</div>
-                  <div v-if="barWidth(line, column)" class="track">
-                    <span :style="{ width: barWidth(line, column)! }" />
-                  </div>
-                </td>
-              </tr>
-            </tbody>
-          </table>
+      <template v-if="rows.length">
+        <div class="stats">
+          <div class="stat">
+            <div class="label">两边都做过的题</div>
+            <div class="value num">{{ rows.length }}<span class="unit"> 道</span></div>
+          </div>
+          <div class="stat">
+            <div class="label">一次就对</div>
+            <div class="value num">
+              {{ summary.now }}%<span class="unit"> / {{ shortOther }} {{ summary.before }}%</span>
+            </div>
+          </div>
+          <div class="stat">
+            <div class="label">比{{ shortOther }}差</div>
+            <div class="value num worse-text">{{ worse.length }}<span class="unit"> 道</span></div>
+          </div>
+          <div class="stat">
+            <div class="label">比{{ shortOther }}好</div>
+            <div class="value num better-text">
+              {{ better.length }}<span class="unit"> 道</span>
+            </div>
+          </div>
         </div>
-      </section>
+
+        <section class="card">
+          <div class="row axis">
+            <span class="c-title" />
+            <span class="c-track ticks num">
+              <span v-for="tick in [0, 25, 50, 75, 100]" :key="tick" :style="{ left: `${tick}%` }"
+                >{{ tick }}%</span
+              >
+            </span>
+            <span class="legend">
+              <span><i class="dot-now" />{{ selected }} 级</span>
+              <span><i class="dot-before" />{{ shortOther }}</span>
+            </span>
+          </div>
+          <template v-for="group in groups" :key="group.key">
+            <div class="group-head">
+              <span class="strong" :class="`${group.key}-text`">{{ group.label }}</span>
+              <span class="muted small num">{{ group.items.length }} 道</span>
+            </div>
+            <div v-for="item in group.items" :key="item.row.id" class="row item">
+              <a :href="problemHref(item.row.displayId)" target="_blank" class="c-title">
+                <span class="muted num pid">{{ item.row.displayId }}</span>
+                <span class="ptitle">{{ item.row.title }}</span>
+              </a>
+              <span class="c-track" :class="tone(item.delta)">
+                <span class="rail" />
+                <span
+                  class="span"
+                  :style="{
+                    left: `${Math.min(item.now, item.before)}%`,
+                    width: `${Math.abs(item.delta)}%`,
+                  }"
+                />
+                <span class="before" :style="{ left: `${item.before}%` }" />
+                <span class="now" :style="{ left: `${item.now}%` }" />
+              </span>
+              <span class="c-values num">
+                <b :class="`${tone(item.delta)}-text`">{{ item.now }}%</b>
+                <span class="muted"> / {{ item.before }}%</span>
+              </span>
+              <span class="c-delta num strong" :class="`${tone(item.delta)}-text`">
+                {{ item.delta > 0 ? "+" : "" }}{{ item.delta }}
+              </span>
+              <span class="c-users muted small num">
+                {{ selected }} 级 {{ item.mine.users }} 人 · {{ shortOther }}
+                {{ item.theirs.users }} 人
+              </span>
+            </div>
+          </template>
+        </section>
+      </template>
+      <n-empty
+        v-else-if="!loading"
+        :description="`${selected ? `${selected} 级` : '这一届'}和${otherLabel}没有都做过（每边 ${MIN_USERS} 人以上）的题`"
+        style="margin: 60px 0"
+      />
     </n-spin>
   </div>
 </template>
 
 <style scoped>
 .page {
+  --worse: #d9730d;
+  --worse-text: #b35c00;
+  --better: #2080f0;
+  --better-text: #1a66c2;
   display: flex;
   flex-direction: column;
   gap: 16px;
 }
+html.dark .page {
+  --worse-text: #f2a65a;
+  --better-text: #70b0ff;
+}
 .top {
   display: flex;
   align-items: center;
-  gap: 12px;
+  gap: 10px;
 }
 .title {
   font-size: 20px;
@@ -186,70 +275,191 @@ onMounted(async () => {
 .muted {
   opacity: 0.6;
 }
+.small {
+  font-size: 12px;
+}
+.strong {
+  font-weight: 700;
+}
 .num {
   font-variant-numeric: tabular-nums;
 }
+.worse-text {
+  color: var(--worse-text);
+}
+.better-text {
+  color: var(--better-text);
+}
+.stats {
+  display: grid;
+  grid-template-columns: 1.4fr 1fr 1fr 1fr;
+  gap: 12px;
+  margin-bottom: 12px;
+}
+.stat {
+  border: 1px solid var(--learn-line);
+  border-radius: 8px;
+  padding: 14px 18px;
+}
+.label {
+  font-size: 13px;
+  opacity: 0.6;
+}
+.value {
+  font-size: 26px;
+  font-weight: 700;
+}
+.unit {
+  font-size: 15px;
+  font-weight: 400;
+  opacity: 0.6;
+}
 .card {
   border: 1px solid var(--learn-line);
   border-radius: 8px;
-  overflow: hidden;
+  padding: 8px 0 6px;
 }
-.scroll {
-  overflow-x: auto;
-}
-table {
-  border-collapse: collapse;
-  width: 100%;
-  min-width: 900px;
-}
-th,
-td {
+.row {
+  display: flex;
+  align-items: center;
+  gap: 14px;
   padding: 0 16px;
-  text-align: right;
-  white-space: nowrap;
 }
-th {
-  height: 56px;
-  font-size: 14px;
-  font-weight: 700;
-  vertical-align: bottom;
-  padding-bottom: 10px;
+.axis {
+  height: 24px;
 }
-td {
-  height: 52px;
+.item {
+  height: 38px;
   border-top: 1px solid var(--learn-line);
 }
-.label {
-  text-align: left;
-  width: 130px;
+.group-head {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 12px 16px 6px;
 }
-th.label {
-  font-size: 12px;
-  font-weight: 400;
+.c-title {
+  width: 270px;
+  flex-shrink: 0;
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  min-width: 0;
+  color: inherit;
+  text-decoration: none;
 }
-.sub {
-  font-size: 12px;
-  font-weight: 400;
+a.c-title:hover .ptitle {
+  color: var(--learn-green-text);
+}
+.pid {
+  width: 34px;
+  flex-shrink: 0;
+}
+.ptitle {
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+.c-track {
+  position: relative;
+  flex: 0 1 420px;
+  min-width: 200px;
+  height: 20px;
+}
+.ticks > span {
+  position: absolute;
+  top: 2px;
+  width: 36px;
+  margin-left: -18px;
+  text-align: center;
+  font-size: 11px;
   opacity: 0.6;
 }
-.current {
-  font-weight: 700;
-  border-left: 1px solid var(--learn-line);
+.rail {
+  position: absolute;
+  left: 0;
+  right: 0;
+  top: 9px;
+  height: 2px;
+  background: var(--learn-line);
 }
-.last {
-  opacity: 0.7;
+.span {
+  position: absolute;
+  top: 8px;
+  height: 4px;
+  border-radius: 2px;
+  opacity: 0.35;
+  background: var(--learn-line);
 }
-.track {
-  margin: 4px 0 0 auto;
-  width: 88px;
-  height: 5px;
-  border-radius: 3px;
-  background: var(--learn-todo);
+.worse .span,
+.worse .now {
+  background: var(--worse);
+}
+.better .span,
+.better .now {
+  background: var(--better);
+}
+.before {
+  position: absolute;
+  top: 4px;
+  width: 12px;
+  height: 12px;
+  margin-left: -6px;
+  border-radius: 6px;
+  box-sizing: border-box;
+  border: 2px solid rgba(128, 128, 128, 0.8);
+  background: var(--learn-pane);
+}
+.now {
+  position: absolute;
+  top: 3px;
+  width: 14px;
+  height: 14px;
+  margin-left: -7px;
+  border-radius: 7px;
+  background: rgba(128, 128, 128, 0.8);
+}
+.c-values {
+  width: 92px;
+  flex-shrink: 0;
+  font-size: 13px;
+  white-space: nowrap;
+}
+.c-delta {
+  width: 44px;
+  flex-shrink: 0;
+  text-align: right;
+}
+.c-users {
+  flex: 1;
+  min-width: 0;
+  white-space: nowrap;
   overflow: hidden;
+  text-overflow: ellipsis;
 }
-.track > span {
-  display: block;
-  height: 100%;
-  background: var(--learn-green-line);
+.legend {
+  display: flex;
+  gap: 14px;
+  margin-left: 16px;
+  font-size: 12px;
+  white-space: nowrap;
+}
+.legend > span {
+  display: inline-flex;
+  align-items: center;
+  gap: 5px;
+}
+.dot-now {
+  width: 10px;
+  height: 10px;
+  border-radius: 5px;
+  background: var(--worse);
+}
+.dot-before {
+  width: 10px;
+  height: 10px;
+  border-radius: 5px;
+  box-sizing: border-box;
+  border: 2px solid rgba(128, 128, 128, 0.8);
 }
 </style>
diff --git a/apps/web/src/routes.ts b/apps/web/src/routes.ts
index be294f9..8055ebc 100644
--- a/apps/web/src/routes.ts
+++ b/apps/web/src/routes.ts
@@ -310,13 +310,11 @@ export const admins: RouteRecordRaw = {
       meta: { requiresTeacherAdmin: true },
     },
     {
-      path: "problem/yearly",
-      name: "admin yearly overview",
-      component: () => import("admin/problem/Yearly.vue"),
+      path: "problem/trend",
+      name: "admin grade trend",
+      component: () => import("admin/problem/Trend.vue"),
       meta: { requiresTeacherAdmin: true },
     },
-    // 「年度趋势」改名「历年概况」之前的地址，收藏夹里可能还有
-    { path: "problem/top_ac_trend", redirect: "/admin/problem/yearly" },
     // 题单管理路由
     {
       path: "problemset/list",
diff --git a/apps/web/src/shared/layout/admin.vue b/apps/web/src/shared/layout/admin.vue
index 84b1ca0..05f3c0a 100644
--- a/apps/web/src/shared/layout/admin.vue
+++ b/apps/web/src/shared/layout/admin.vue
@@ -85,9 +85,9 @@ const NAV: NavGroup[] = [
         role: "teacher",
       },
       {
-        label: "历年概况",
+        label: "年度趋势",
         icon: "ph:chart-line-up",
-        path: "/admin/problem/yearly",
+        path: "/admin/problem/trend",
         role: "teacher",
       },
       { label: "自学情况", icon: "ph:student", path: "/admin/learn", role: "teacher" },
diff --git a/apps/web/src/utils/types.ts b/apps/web/src/utils/types.ts
index 0ac569c..3c7b709 100644
--- a/apps/web/src/utils/types.ts
+++ b/apps/web/src/utils/types.ts
@@ -330,8 +330,7 @@ export type {
   StuckProblem,
   StuckProblemDetail,
   StuckStudent,
-  YearlyOverview,
-  YearlySummary,
+  GradeTrendProblem,
   LearnBoard,
   LearnBoardStudent,
   LearnExerciseProgress,