diff --git a/schema.sql b/schema.sql
index d9fdf4b..ee5669d 100644
--- a/schema.sql
+++ b/schema.sql
@@ -19,22 +19,37 @@ CREATE TABLE IF NOT EXISTS projects (
   repo_url    text DEFAULT '',             -- Gitea repo
   app_url     text DEFAULT '',             -- 배포된 앱 (*.apps.bokdev.in)
   tags        text DEFAULT '',             -- 콤마 구분
+  is_public   boolean NOT NULL DEFAULT true, -- 공개(피드 노출) / 비공개(나만)
+  lang        text DEFAULT '',             -- 대표 언어(태그에서 추론, 카드 언어 점)
   created_at  timestamptz NOT NULL DEFAULT now(),
   updated_at  timestamptz NOT NULL DEFAULT now()
 );
+-- 기존 배포 DB 대비 멱등 컬럼 추가
+ALTER TABLE projects ADD COLUMN IF NOT EXISTS is_public boolean NOT NULL DEFAULT true;
+ALTER TABLE projects ADD COLUMN IF NOT EXISTS lang text DEFAULT '';
 CREATE INDEX IF NOT EXISTS idx_projects_created ON projects(created_at DESC);
 
--- 코멘트
+-- 코멘트 (parent_id 가 null 이면 최상위, 있으면 대댓글 — 1뎁스만 허용: 앱에서 검증)
 CREATE TABLE IF NOT EXISTS comments (
   id          bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
   project_id  bigint NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
   author_sabun text NOT NULL REFERENCES users(sabun),
+  parent_id   bigint REFERENCES comments(id) ON DELETE CASCADE,
   body        text NOT NULL,
   created_at  timestamptz NOT NULL DEFAULT now()
 );
+ALTER TABLE comments ADD COLUMN IF NOT EXISTS parent_id bigint REFERENCES comments(id) ON DELETE CASCADE;
 CREATE INDEX IF NOT EXISTS idx_comments_project ON comments(project_id, created_at);
 
--- 스타(좋아요)
+-- 좋아요(❤️) — 1인 1좋아요
+CREATE TABLE IF NOT EXISTS hearts (
+  project_id  bigint NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  sabun       text NOT NULL REFERENCES users(sabun),
+  created_at  timestamptz NOT NULL DEFAULT now(),
+  PRIMARY KEY (project_id, sabun)
+);
+
+-- 즐겨찾기(⭐ Star) — 1인 1즐겨찾기
 CREATE TABLE IF NOT EXISTS stars (
   project_id  bigint NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
   sabun       text NOT NULL REFERENCES users(sabun),
diff --git a/src/db.js b/src/db.js
index 795d0fc..db0bf4d 100644
--- a/src/db.js
+++ b/src/db.js
@@ -17,28 +17,36 @@ export async function upsertUser({ sabun, name, email }) {
   );
 }
 
-// 프로젝트 목록 (스타 수 + 코멘트 수 + 소유자 이름 포함)
-export async function listProjects() {
+// 카드/피드에 필요한 카운트 + 현재 사용자(viewer)의 ❤️/⭐ 여부를 함께 계산하는 공통 SELECT 절.
+// $1 = viewer 사번.
+const PROJECT_SELECT = `
+  SELECT p.*, u.name AS owner_name,
+         (SELECT count(*) FROM hearts  h WHERE h.project_id=p.id)::int AS heart_count,
+         (SELECT count(*) FROM stars   s WHERE s.project_id=p.id)::int AS star_count,
+         (SELECT count(*) FROM comments c WHERE c.project_id=p.id)::int AS comment_count,
+         EXISTS(SELECT 1 FROM hearts h WHERE h.project_id=p.id AND h.sabun=$1) AS hearted,
+         EXISTS(SELECT 1 FROM stars  s WHERE s.project_id=p.id AND s.sabun=$1) AS starred
+    FROM projects p JOIN users u ON u.sabun=p.owner_sabun`;
+
+// 프로젝트 목록 — 공개 프로젝트 + viewer 본인의 비공개 프로젝트.
+// (남의 비공개는 절대 반환하지 않음) 피드/내프로젝트 분리는 호출부(server.js)에서.
+export async function listProjects(viewer) {
   const { rows } = await q(
-    `SELECT p.*, u.name AS owner_name,
-            (SELECT count(*) FROM stars s WHERE s.project_id=p.id) AS star_count,
-            (SELECT count(*) FROM comments c WHERE c.project_id=p.id) AS comment_count
-       FROM projects p JOIN users u ON u.sabun=p.owner_sabun
-      ORDER BY p.created_at DESC`
+    `${PROJECT_SELECT}
+      WHERE p.is_public OR p.owner_sabun=$1
+      ORDER BY p.created_at DESC`,
+    [viewer]
   );
   return rows;
 }
 
-export async function getProject(id) {
-  const { rows } = await q(
-    `SELECT p.*, u.name AS owner_name,
-            (SELECT count(*) FROM stars s WHERE s.project_id=p.id) AS star_count
-       FROM projects p JOIN users u ON u.sabun=p.owner_sabun WHERE p.id=$1`,
-    [id]
-  );
+// 단일 프로젝트 (가시성 검사는 호출부에서: is_public 이거나 본인일 때만 노출)
+export async function getProject(id, viewer) {
+  const { rows } = await q(`${PROJECT_SELECT} WHERE p.id=$2`, [viewer, id]);
   return rows[0];
 }
 
+// 댓글 목록 (parent_id 포함, 작성 순서). 스레드 구성은 뷰에서.
 export async function listComments(projectId) {
   const { rows } = await q(
     `SELECT c.*, u.name AS author_name
@@ -49,30 +57,80 @@ export async function listComments(projectId) {
   return rows;
 }
 
-export async function addProject({ owner, title, description, repoUrl, appUrl, tags }) {
+export async function addProject({ owner, title, description, repoUrl, appUrl, tags, isPublic, lang }) {
   const { rows } = await q(
-    `INSERT INTO projects (owner_sabun, title, description, repo_url, app_url, tags)
-     VALUES ($1,$2,$3,$4,$5,$6) RETURNING id`,
-    [owner, title, description || "", repoUrl || "", appUrl || "", tags || ""]
+    `INSERT INTO projects (owner_sabun, title, description, repo_url, app_url, tags, is_public, lang)
+     VALUES ($1,$2,$3,$4,$5,$6,$7,$8) RETURNING id`,
+    [owner, title, description || "", repoUrl || "", appUrl || "", tags || "", isPublic !== false, lang || ""]
   );
   return rows[0].id;
 }
 
-export async function addComment({ projectId, author, body }) {
-  await q(`INSERT INTO comments (project_id, author_sabun, body) VALUES ($1,$2,$3)`,
-    [projectId, author, body]);
+// 본인 프로젝트 삭제. 삭제 행 수 반환(0이면 권한 없음/없음).
+export async function deleteProject({ id, sabun }) {
+  const { rowCount } = await q(
+    `DELETE FROM projects WHERE id=$1 AND owner_sabun=$2`,
+    [id, sabun]
+  );
+  return rowCount;
 }
 
+// 공개/비공개 전환 (본인만). 적용 행 수 반환.
+export async function setVisibility({ id, sabun, isPublic }) {
+  const { rowCount } = await q(
+    `UPDATE projects SET is_public=$3, updated_at=now() WHERE id=$1 AND owner_sabun=$2`,
+    [id, sabun, !!isPublic]
+  );
+  return rowCount;
+}
+
+// 댓글/대댓글 작성. parentId 가 있으면 대댓글.
+// 1뎁스 강제: 부모 댓글이 같은 프로젝트의 "최상위(parent_id IS NULL)" 일 때만 허용.
+// 반환: 새 댓글 행(작성자 이름 포함). 거부 시 null.
+export async function addComment({ projectId, author, body, parentId }) {
+  let parent = null;
+  if (parentId) {
+    const { rows } = await q(
+      `SELECT id FROM comments WHERE id=$1 AND project_id=$2 AND parent_id IS NULL`,
+      [parentId, projectId]
+    );
+    if (!rows[0]) return null; // 대댓글에 또 답글(2뎁스) 또는 잘못된 부모 → 거부
+    parent = parentId;
+  }
+  const { rows } = await q(
+    `INSERT INTO comments (project_id, author_sabun, parent_id, body)
+     VALUES ($1,$2,$3,$4) RETURNING *`,
+    [projectId, author, parent, body]
+  );
+  const c = rows[0];
+  const { rows: u } = await q(`SELECT name FROM users WHERE sabun=$1`, [author]);
+  c.author_name = u[0] ? u[0].name : author;
+  return c;
+}
+
+// 본인 댓글 삭제 (자식 대댓글은 FK ON DELETE CASCADE 로 함께 삭제). 삭제 행 수 반환.
+export async function deleteComment({ id, sabun }) {
+  const { rowCount } = await q(
+    `DELETE FROM comments WHERE id=$1 AND author_sabun=$2`,
+    [id, sabun]
+  );
+  return rowCount;
+}
+
+// ❤️ 좋아요 토글 → { on, count }
+export async function toggleHeart({ projectId, sabun }) {
+  const { rowCount } = await q(`DELETE FROM hearts WHERE project_id=$1 AND sabun=$2`, [projectId, sabun]);
+  const on = rowCount === 0;
+  if (on) await q(`INSERT INTO hearts (project_id, sabun) VALUES ($1,$2)`, [projectId, sabun]);
+  const { rows } = await q(`SELECT count(*)::int AS c FROM hearts WHERE project_id=$1`, [projectId]);
+  return { on, count: rows[0].c };
+}
+
+// ⭐ 즐겨찾기(Star) 토글 → { on, count }
 export async function toggleStar({ projectId, sabun }) {
   const { rowCount } = await q(`DELETE FROM stars WHERE project_id=$1 AND sabun=$2`, [projectId, sabun]);
-  if (rowCount === 0) {
-    await q(`INSERT INTO stars (project_id, sabun) VALUES ($1,$2)`, [projectId, sabun]);
-    return true;
-  }
-  return false;
-}
-
-export async function isStarred({ projectId, sabun }) {
-  const { rowCount } = await q(`SELECT 1 FROM stars WHERE project_id=$1 AND sabun=$2`, [projectId, sabun]);
-  return rowCount > 0;
+  const on = rowCount === 0;
+  if (on) await q(`INSERT INTO stars (project_id, sabun) VALUES ($1,$2)`, [projectId, sabun]);
+  const { rows } = await q(`SELECT count(*)::int AS c FROM stars WHERE project_id=$1`, [projectId]);
+  return { on, count: rows[0].c };
 }