diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 5de00a8..60f5a81 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -93,10 +93,10 @@ jobs:
         go get ./...
     - name: Run examples 1
       run: |
-        xvfb-run --auto-servernum --server-num=1 go run . -s 120 -d _examples/base -x params.Termination.MaxTicks=365
-        go run . -r 5 -d _examples/base -e experiment.json -x params.Termination.MaxTicks=365
-        xvfb-run --auto-servernum --server-num=1 go run . -s 120 -d _examples/patches -x params.Termination.MaxTicks=365
-        xvfb-run --auto-servernum --server-num=1 go run . -s 120 -d _examples/weather_file -x params.Termination.MaxTicks=730
-        xvfb-run --auto-servernum --server-num=1 go run . -s 120 -d _examples/weather_builtin -x params.Termination.MaxTicks=730
-        xvfb-run --auto-servernum --server-num=1 go run . -s 120 -d _examples/systems --systems systems.json -x params.Termination.MaxTicks=730
-        go run . -d _examples/systems --systems systems.json -e experiment.json -r 10
+        xvfb-run --auto-servernum --server-num=1 go run . --tps 120 -d _examples/base -x params.Termination.MaxTicks=365
+        go run . -r 5 -d _examples/base -e -x params.Termination.MaxTicks=365
+        xvfb-run --auto-servernum --server-num=1 go run . --tps 120 -d _examples/patches -o -x params.Termination.MaxTicks=365
+        xvfb-run --auto-servernum --server-num=1 go run . --tps 120 -d _examples/weather_file -o -x params.Termination.MaxTicks=730
+        xvfb-run --auto-servernum --server-num=1 go run . --tps 120 -d _examples/weather_builtin -o -x params.Termination.MaxTicks=730
+        xvfb-run --auto-servernum --server-num=1 go run . --tps 120 -d _examples/systems -o -s -x params.Termination.MaxTicks=730
+        go run . -d _examples/systems -o -s -e -r 10
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe3d047..86ae524 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Adds support for seasonal and "scripted" patch dynamics (#23)
 - Adds support for weather/foraging period files (#24)
 - Adds support for adding custom resources/parameters as well as systems (#25)
+- Rework of the command line interface for a simpler syntax when using default file names (#29)
 
 ### Other
 
diff --git a/README.md b/README.md
index 8f2023f..02ea319 100644
--- a/README.md
+++ b/README.md
@@ -30,16 +30,16 @@ Get CLI help like this:
 beecs-cli -h
 ```
 
-A single, slowed down run of the base example, with live plots:
+A single simulation with live plots, at 30 ticks per second:
 
 ```
-beecs-cli -s 30 -d _examples/base
+beecs-cli -d _examples/base --observers --tps 30
 ```
 
 Run the full base example with parameter variation and 10 runs per parameter set:
 
 ```
-beecs-cli -r 10 -d _examples/base -e experiment.json
+beecs-cli -d _examples/base --experiment -r 10
 ```
 
 Print all default parameters in the tool's input format:
@@ -76,7 +76,7 @@ The default is file `parameters.json` in the working directory. Here is an examp
 
 For any kind of output, an **observers file** is required.
 It specifies which observers for visualizations or file output should be used.
-The default is file `parameters.json` in the working directory. Here is an example:
+Here is an example:
 
 ```json
 {
@@ -90,6 +90,8 @@ The default is file `parameters.json` in the working directory. Here is an examp
 }
 ```
 
+Observers must be enabled using the `-o` flag. The default is file `observers.json` in the working directory. 
+
 These files are sufficient for single simulations with visual of file output.
 
 With a further **experiment file**, parameters can be systematically varied in various ways.
@@ -114,6 +116,8 @@ Here is an example:
 ]
 ```
 
+Experiments must be enabled using the `-e` flag. The default is file `experiments.json` in the working directory.
+
 > Note: The prefix `params.` is required to unambiguously identify the type of the parameter group to modify.
 
 See also the [examples](https://github.com/mlange-42/beecs-cli/tree/main/_examples) for the format of the required JSON files.
diff --git a/cli/cli.go b/cli/cli.go
index a2030d0..ddfcfee 100644
--- a/cli/cli.go
+++ b/cli/cli.go
@@ -18,6 +18,7 @@ import (
 	"github.com/mlange-42/beecs/experiment"
 	baseparams "github.com/mlange-42/beecs/params"
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 	"golang.org/x/exp/rand"
 )
 
@@ -25,6 +26,7 @@ const (
 	_PARAMETERS = "parameters.json"
 	_OBSERVERS  = "observers.json"
 	_EXPERIMENT = "experiment.json"
+	_SYSTEMS    = "systems.json"
 )
 
 func Run() {
@@ -40,16 +42,17 @@ func rootCommand() *cobra.Command {
 	var dir string
 	var outDir string
 	var paramFiles []string
-	var expFile string
-	var obsFile string
-	var sysFile string
+	var expFile []string
+	var obsFile []string
+	var sysFile []string
 	var speed float64
 	var threads int
 	var runs int
 	var overwrite []string
 	var seed int
 
-	root := &cobra.Command{
+	var root cobra.Command
+	root = cobra.Command{
 		Use:           "beecs-cli",
 		Short:         "beecs-cli provides a command line interface for the beecs model.",
 		Long:          `beecs-cli provides a command line interface for the beecs model.`,
@@ -64,6 +67,11 @@ func rootCommand() *cobra.Command {
 				os.Exit(0)
 			}
 
+			flagUsed := map[string]bool{}
+			root.Flags().Visit(func(f *pflag.Flag) {
+				flagUsed[f.Name] = true
+			})
+
 			rand.Seed(uint64(time.Now().UTC().Nanosecond()))
 
 			if outDir == "" {
@@ -90,8 +98,11 @@ func rootCommand() *cobra.Command {
 
 			var exp experiment.Experiment
 			var err error
-			if expFile != "" {
-				exp, err = util.ExperimentFromFile(path.Join(dir, expFile))
+			if flagUsed["experiment"] {
+				if len(expFile) > 1 {
+					return fmt.Errorf("only one (optional) experiment file can be used")
+				}
+				exp, err = util.ExperimentFromFile(path.Join(dir, expFile[0]))
 				if err != nil {
 					return err
 				}
@@ -103,15 +114,21 @@ func rootCommand() *cobra.Command {
 			}
 
 			var observers util.ObserversDef
-			if obsFile != "" {
-				observers, err = util.ObserversDefFromFile(path.Join(dir, obsFile))
+			if flagUsed["observers"] {
+				if len(obsFile) > 1 {
+					return fmt.Errorf("only one (optional) observers file can be used")
+				}
+				observers, err = util.ObserversDefFromFile(path.Join(dir, obsFile[0]))
 				if err != nil {
 					return err
 				}
 			}
 			var systems []model.System
-			if sysFile != "" {
-				systems, err = util.SystemsFromFile(path.Join(dir, sysFile))
+			if flagUsed["systems"] {
+				if len(sysFile) > 1 {
+					return fmt.Errorf("only one (optional) systems file can be used")
+				}
+				systems, err = util.SystemsFromFile(path.Join(dir, sysFile[0]))
 				if err != nil {
 					return err
 				}
@@ -147,11 +164,21 @@ func rootCommand() *cobra.Command {
 
 	root.Flags().StringVarP(&dir, "directory", "d", ".", "Working directory")
 	root.Flags().StringVarP(&outDir, "output", "", "", "Output directory if different from working directory")
-	root.Flags().StringSliceVarP(&paramFiles, "parameters", "p", []string{_PARAMETERS}, "Parameter files, processed in the given order")
-	root.Flags().StringVarP(&expFile, "experiment", "e", "", "Experiment file for parameter variation")
-	root.Flags().StringVarP(&obsFile, "observers", "o", _OBSERVERS, "Observers file for adding observers")
-	root.Flags().StringVarP(&sysFile, "systems", "", "", "Systems file for using custom systems or changing the scheduling")
-	root.Flags().Float64VarP(&speed, "speed", "s", 0, "Speed limit in ticks per second. Default: 0 (unlimited)")
+	root.Flags().StringSliceVarP(&paramFiles, "parameters", "p", []string{_PARAMETERS}, "Parameter files, processed in the given order\n")
+
+	root.Flags().StringSliceVarP(&expFile, "experiment", "e", []string{_EXPERIMENT},
+		"Run experiment. Optionally one experiment file for parameter variation\n")
+	root.Flag("experiment").NoOptDefVal = _EXPERIMENT
+
+	root.Flags().StringSliceVarP(&obsFile, "observers", "o", []string{_OBSERVERS},
+		"Run with observers. Optionally one observers file for adding observers\n")
+	root.Flag("observers").NoOptDefVal = _OBSERVERS
+
+	root.Flags().StringSliceVarP(&sysFile, "systems", "s", []string{_SYSTEMS},
+		"Run with custom systems. Optionally one systems file for using custom systems or changing the scheduling\n")
+	root.Flag("systems").NoOptDefVal = _SYSTEMS
+
+	root.Flags().Float64VarP(&speed, "tps", "", 0, "Speed limit in ticks per second. Default: 0 (unlimited)")
 	root.Flags().IntVarP(&threads, "threads", "t", runtime.NumCPU(), "Number of threads")
 	root.Flags().IntVarP(&runs, "runs", "r", 1, "Runs per parameter set")
 	root.Flags().IntVarP(&seed, "seed", "", 0, "Super random seed for seed generation. Default: 0 (unseeded)")
@@ -160,7 +187,7 @@ func rootCommand() *cobra.Command {
 	root.AddCommand(initCommand())
 	root.AddCommand(parametersCommand())
 
-	return root
+	return &root
 }
 
 func parametersCommand() *cobra.Command {
diff --git a/go.mod b/go.mod
index 8d76c89..5c43694 100644
--- a/go.mod
+++ b/go.mod
@@ -8,6 +8,7 @@ require (
 	github.com/mlange-42/arche-pixel v0.9.0
 	github.com/mlange-42/beecs v0.1.1-0.20240520193329-cfbd62899b75
 	github.com/spf13/cobra v1.8.0
+	github.com/spf13/pflag v1.0.5
 	golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa
 )
 
@@ -31,7 +32,6 @@ require (
 	github.com/mazznoer/csscolorparser v0.1.2 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/image v0.15.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	gonum.org/v1/gonum v0.15.0 // indirect