diff --git a/Makefile b/Makefile
index 79c0ab6..45f79e1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,10 @@
 .PHONY: all clean
 
 BUILD_DIR = ./build
+APP_NAME = joj3
 
 all:
-	go build -o $(BUILD_DIR)/tiger ./cmd/tiger
+	go build -o $(BUILD_DIR)/$(APP_NAME) ./cmd/$(APP_NAME)
 
 clean:
 	rm -rf $(BUILD_DIR)/*
diff --git a/README.md b/README.md
index b6e67cc..edbaba6 100644
--- a/README.md
+++ b/README.md
@@ -1,20 +1,10 @@
 # JOJ3
 
-## Try `tiger`
-
 ```bash
-$ make clean && make && sudo ./build/tiger python3 -c 'bytearray(1024 * 1024); 10 ** 10 ** 3; print("out"); import sys; print("err", file=sys.stderr)'
+$ make clean && make && ./build/joj3
 rm -rf ./build/*
 rm -rf *.out
-go build -o ./build/tiger ./cmd/tiger
-2024/03/01 01:25:34 INFO process created pid=3148763
-2024/03/01 01:25:34 INFO done success time=16.80708ms
-ReturnCode: 0
-Stdout: out
-
-Stderr: err
-
-TimedOut: false
-TimeNs: 0
-MemoryByte: 0
+go build -o ./build/joj3 ./cmd/joj3
+dummy stage 0: score: 0, comment: I'm a dummy
+dummy stage 1: score: 0, comment: I'm a dummy
 ```
diff --git a/cmd/joj3/main.go b/cmd/joj3/main.go
new file mode 100644
index 0000000..a48f167
--- /dev/null
+++ b/cmd/joj3/main.go
@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+
+	_ "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/executors"
+	_ "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/parsers"
+	"focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/stage"
+)
+
+func main() {
+	stages := stage.ParseStages()
+	results := stage.Run(stages)
+	for _, result := range results {
+		fmt.Printf(
+			"%s: score: %d, comment: %s\n",
+			result.Name, result.Score, result.Comment,
+		)
+	}
+}
diff --git a/cmd/tiger/root.go b/cmd/tiger/root.go
deleted file mode 100644
index 35a4cdf..0000000
--- a/cmd/tiger/root.go
+++ /dev/null
@@ -1,26 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"os"
-
-	"focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/pkg/runner"
-)
-
-func main() {
-	if len(os.Args) < 2 {
-		fmt.Println("usage: " + os.Args[0] + " <command>")
-		os.Exit(1)
-	}
-	// hard limit of timeout 1000ms
-	runResult, err := runner.RunInCgroupsV1(os.Args[1:], "nobody", "/joj3.tiger", 1000)
-	if err != nil {
-		fmt.Printf("Error: %v\n", err)
-	}
-	fmt.Printf("ReturnCode: %d\n", runResult.ReturnCode)
-	fmt.Printf("Stdout: %s\n", runResult.Stdout)
-	fmt.Printf("Stderr: %s\n", runResult.Stderr)
-	fmt.Printf("TimedOut: %v\n", runResult.TimedOut)
-	fmt.Printf("TimeNs: %v\n", runResult.TimeNs)
-	fmt.Printf("MemoryByte: %v\n", runResult.MemoryByte)
-}
diff --git a/go.mod b/go.mod
index d0fd59b..18c2a21 100644
--- a/go.mod
+++ b/go.mod
@@ -2,15 +2,11 @@ module focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3
 
 go 1.22.0
 
-require (
-	github.com/containerd/cgroups v1.1.0
-	github.com/opencontainers/runtime-spec v1.2.0
-)
+require github.com/criyle/go-judge v1.8.1
 
 require (
-	github.com/coreos/go-systemd/v22 v22.3.2 // indirect
-	github.com/docker/go-units v0.4.0 // indirect
-	github.com/godbus/dbus/v5 v5.0.4 // indirect
-	github.com/gogo/protobuf v1.3.2 // indirect
-	golang.org/x/sys v0.0.0-20210906170528-6f6e22806c34 // indirect
+	github.com/creack/pty v1.1.21 // indirect
+	github.com/criyle/go-sandbox v0.10.1 // indirect
+	golang.org/x/sync v0.6.0 // indirect
+	golang.org/x/sys v0.16.0 // indirect
 )
diff --git a/go.sum b/go.sum
index bb37a6f..ad35e91 100644
--- a/go.sum
+++ b/go.sum
@@ -1,43 +1,10 @@
-github.com/containerd/cgroups v1.1.0 h1:v8rEWFl6EoqHB+swVNjVoCJE8o3jX7e8nqBGPLaDFBM=
-github.com/containerd/cgroups v1.1.0/go.mod h1:6ppBcbh/NOOUU+dMKrykgaBnK9lCIBxHqJDGwsa1mIw=
-github.com/coreos/go-systemd/v22 v22.3.2 h1:D9/bQk5vlXQFZ6Kwuu6zaiXJ9oTPe68++AzAJc1DzSI=
-github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
-github.com/docker/go-units v0.4.0 h1:3uh0PgVws3nIA0Q+MwDC8yjEPf9zjRfZZWXZYDct3Tw=
-github.com/docker/go-units v0.4.0/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
-github.com/godbus/dbus/v5 v5.0.4 h1:9349emZab16e7zQvpmsbtjc18ykshndd8y2PG3sgJbA=
-github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
-github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
-github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69NZV8Q=
-github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
-github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
-github.com/opencontainers/runtime-spec v1.2.0 h1:z97+pHb3uELt/yiAWD691HNHQIF07bE7dzrbT927iTk=
-github.com/opencontainers/runtime-spec v1.2.0/go.mod h1:jwyrGlmzljRJv/Fgzds9SsS/C5hL+LL3ko9hs6T5lQ0=
-github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210906170528-6f6e22806c34 h1:GkvMjFtXUmahfDtashnc1mnrCtuBVcwse5QV2lUk/tI=
-golang.org/x/sys v0.0.0-20210906170528-6f6e22806c34/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
-golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+github.com/creack/pty v1.1.21 h1:1/QdRyBaHHJP61QkWMXlOIBfsgdDeeKfK8SYVUWJKf0=
+github.com/creack/pty v1.1.21/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
+github.com/criyle/go-judge v1.8.1 h1:VI9OGz1MnLp9cv//gMVL8uruNwxSod5UmNwew8ZnfCA=
+github.com/criyle/go-judge v1.8.1/go.mod h1:yZepeuMTmQXEJnBgHZQIGVuytRYWlLhQBQHLaL84N5w=
+github.com/criyle/go-sandbox v0.10.1 h1:z9Il/UXQwKEvIwdr1wVheWWWAqGWtdTItBmEsWqFqT4=
+github.com/criyle/go-sandbox v0.10.1/go.mod h1:ivPw/HEh5unxVRlXJxCgkgTCuy+cxTkQDX7D2XQf/kg=
+golang.org/x/sync v0.6.0 h1:5BMeUDZ7vkXGfEr1x9B4bRcTH4lpkTkpdh0T/J+qjbQ=
+golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
+golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
diff --git a/internal/app/healthcheck/main.go b/internal/app/healthcheck/main.go
new file mode 100644
index 0000000..9b4e3b7
--- /dev/null
+++ b/internal/app/healthcheck/main.go
@@ -0,0 +1 @@
+package healthcheck
diff --git a/internal/executors/all.go b/internal/executors/all.go
new file mode 100644
index 0000000..706ba7b
--- /dev/null
+++ b/internal/executors/all.go
@@ -0,0 +1,8 @@
+package executors
+
+import (
+	_ "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/executors/dummy"
+)
+
+// this file does nothing but imports to ensure all the init() functions
+// in the subpackages are called
diff --git a/internal/executors/dummy/executor.go b/internal/executors/dummy/executor.go
new file mode 100644
index 0000000..5c8b296
--- /dev/null
+++ b/internal/executors/dummy/executor.go
@@ -0,0 +1,21 @@
+package dummy
+
+import (
+	"github.com/criyle/go-judge/cmd/go-judge/model"
+	"github.com/criyle/go-judge/envexec"
+)
+
+type Dummy struct{}
+
+func (e *Dummy) Run(model.Cmd) model.Result {
+	return model.Result{
+		Status:     model.Status(envexec.StatusInvalid),
+		ExitStatus: 0,
+		Error:      "I'm a dummy",
+		Time:       0,
+		Memory:     0,
+		RunTime:    0,
+		Files:      map[string]string{},
+		FileIDs:    map[string]string{},
+	}
+}
diff --git a/internal/executors/dummy/meta.go b/internal/executors/dummy/meta.go
new file mode 100644
index 0000000..e687e52
--- /dev/null
+++ b/internal/executors/dummy/meta.go
@@ -0,0 +1,9 @@
+package dummy
+
+import "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/stage"
+
+var name = "dummy"
+
+func init() {
+	stage.RegisterExecutor(name, &Dummy{})
+}
diff --git a/internal/parsers/all.go b/internal/parsers/all.go
new file mode 100644
index 0000000..5ee6a62
--- /dev/null
+++ b/internal/parsers/all.go
@@ -0,0 +1,8 @@
+package parsers
+
+import (
+	_ "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/parsers/dummy"
+)
+
+// this file does nothing but imports to ensure all the init() functions
+// in the subpackages are called
diff --git a/internal/parsers/dummy/meta.go b/internal/parsers/dummy/meta.go
new file mode 100644
index 0000000..fd9ba75
--- /dev/null
+++ b/internal/parsers/dummy/meta.go
@@ -0,0 +1,9 @@
+package dummy
+
+import "focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/stage"
+
+var name = "dummy"
+
+func init() {
+	stage.RegisterParser(name, &Dummy{})
+}
diff --git a/internal/parsers/dummy/parser.go b/internal/parsers/dummy/parser.go
new file mode 100644
index 0000000..89e6bb1
--- /dev/null
+++ b/internal/parsers/dummy/parser.go
@@ -0,0 +1,15 @@
+package dummy
+
+import (
+	"focs.ji.sjtu.edu.cn/git/FOCS-dev/JOJ3/internal/stage"
+	"github.com/criyle/go-judge/cmd/go-judge/model"
+)
+
+type Dummy struct{}
+
+func (e *Dummy) Run(result model.Result, config string) stage.ParserResult {
+	return stage.ParserResult{
+		Score:   0,
+		Comment: "I'm a dummy",
+	}
+}
diff --git a/internal/stage/executor.go b/internal/stage/executor.go
new file mode 100644
index 0000000..ecf09d7
--- /dev/null
+++ b/internal/stage/executor.go
@@ -0,0 +1,15 @@
+package stage
+
+import (
+	"github.com/criyle/go-judge/cmd/go-judge/model"
+)
+
+var executorMap = map[string]Executor{}
+
+type Executor interface {
+	Run(model.Cmd) model.Result
+}
+
+func RegisterExecutor(name string, executor Executor) {
+	executorMap[name] = executor
+}
diff --git a/internal/stage/parser.go b/internal/stage/parser.go
new file mode 100644
index 0000000..43f3994
--- /dev/null
+++ b/internal/stage/parser.go
@@ -0,0 +1,18 @@
+package stage
+
+import "github.com/criyle/go-judge/cmd/go-judge/model"
+
+var parserMap = map[string]Parser{}
+
+type Parser interface {
+	Run(model.Result, string) ParserResult
+}
+
+type ParserResult struct {
+	Score   int
+	Comment string
+}
+
+func RegisterParser(name string, parser Parser) {
+	parserMap[name] = parser
+}
diff --git a/internal/stage/run.go b/internal/stage/run.go
new file mode 100644
index 0000000..fcb92a2
--- /dev/null
+++ b/internal/stage/run.go
@@ -0,0 +1,49 @@
+package stage
+
+import (
+	"github.com/criyle/go-judge/cmd/go-judge/model"
+)
+
+type Stage struct {
+	name         string
+	executor     Executor
+	executorCmd  model.Cmd
+	parser       Parser
+	parserConfig string
+}
+
+type StageResult struct {
+	Name string
+	ParserResult
+}
+
+func ParseStages() []Stage {
+	stages := []Stage{}
+	config := [][]string{
+		{"dummy stage 0", "dummy", "dummy"},
+		{"dummy stage 1", "dummy", "dummy"},
+	}
+	for _, v := range config {
+		stages = append(stages, Stage{
+			name:         v[0],
+			executor:     executorMap[v[1]],
+			executorCmd:  model.Cmd{},
+			parser:       parserMap[v[2]],
+			parserConfig: "",
+		})
+	}
+	return stages
+}
+
+func Run(stages []Stage) []StageResult {
+	var parserResults []StageResult
+	for _, stage := range stages {
+		executorResult := stage.executor.Run(stage.executorCmd)
+		parserResult := stage.parser.Run(executorResult, stage.parserConfig)
+		parserResults = append(parserResults, StageResult{
+			Name:         stage.name,
+			ParserResult: parserResult,
+		})
+	}
+	return parserResults
+}
diff --git a/pkg/runner/root.go b/pkg/runner/root.go
deleted file mode 100644
index 95f026d..0000000
--- a/pkg/runner/root.go
+++ /dev/null
@@ -1,96 +0,0 @@
-package runner
-
-import (
-	"bytes"
-	"log/slog"
-	"os/exec"
-	"os/user"
-	"strconv"
-	"syscall"
-	"time"
-
-	"github.com/containerd/cgroups"
-	"github.com/opencontainers/runtime-spec/specs-go"
-)
-
-type RunResult struct {
-	ReturnCode int
-	Stdout     []byte
-	Stderr     []byte
-	TimedOut   bool
-	TimeNs     uint64
-	MemoryByte uint64
-}
-
-func RunInCgroupsV1(
-	args []string, username string, cgroupsPath string, timeoutMs uint,
-) (result *RunResult, err error) {
-	u, err := user.Lookup(username)
-	if err != nil {
-		return
-	}
-	control, err := cgroups.New(
-		cgroups.V1,
-		cgroups.StaticPath(cgroupsPath),
-		&specs.LinuxResources{},
-	)
-	if err != nil {
-		return
-	}
-	defer func() {
-		if err := control.Delete(); err != nil {
-			slog.Error("control.Delete", "error", err)
-		}
-	}()
-	cmd := exec.Command(args[0], args[1:]...)
-	cmd.SysProcAttr = &syscall.SysProcAttr{}
-	uid, _ := strconv.ParseUint(u.Uid, 10, 32)
-	gid, _ := strconv.ParseUint(u.Gid, 10, 32)
-	cmd.SysProcAttr.Credential = &syscall.Credential{Uid: uint32(uid), Gid: uint32(gid)}
-	var stdout, stderr bytes.Buffer
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
-	start := time.Now()
-	err = cmd.Start()
-	if err != nil {
-		return
-	}
-	pid := cmd.Process.Pid
-	slog.Info("process created", "pid", strconv.Itoa(pid))
-	if err = control.Add(cgroups.Process{Pid: pid}); err != nil {
-		return
-	}
-	var returnCode int
-	exitCode := make(chan int, 1)
-	go func(exit_code chan int) {
-		if err = cmd.Wait(); err != nil {
-			exit_code <- err.(*exec.ExitError).ExitCode()
-		} else {
-			exit_code <- 0
-		}
-	}(exitCode)
-	timeoutLimit := time.Duration(timeoutMs) * time.Millisecond
-	timedOut := false
-	select {
-	case returnCode = <-exitCode:
-		slog.Info("done success", "time", time.Since(start))
-	case <-time.After(timeoutLimit):
-		slog.Info("done timeout", "time", time.Since(start))
-		_ = cmd.Process.Kill()
-		returnCode = <-exitCode
-		timedOut = true
-	}
-	stats, err := control.Stat(cgroups.IgnoreNotExist)
-	if err != nil {
-		return
-	}
-	result = &RunResult{
-		ReturnCode: returnCode,
-		Stdout:     stdout.Bytes(),
-		Stderr:     stderr.Bytes(),
-		TimedOut:   timedOut,
-		TimeNs:     stats.CPU.Usage.Kernel + stats.CPU.Usage.User,
-		MemoryByte: stats.Memory.Usage.Max, // Memory.Usage.Max = 0 when killed
-	}
-	return
-}