diff --git a/README.md b/README.md
index 7431ddc..14e07af 100644
--- a/README.md
+++ b/README.md
@@ -62,8 +62,8 @@ There are other commands implemented as well, e.g. for changing the brightness.
 - runs all game logic
 - sends image and text to the service point display
 - sends image to clients
-- currently, the game has a fixed tick and frame rate of 25/s
-- One frame is ~7KB, not including the text
+- The game has a dynamic update rate. Hundreds of updates per second on a laptop are expected.
+- One frame is ~7KB, not including the text and player specific data
 - maps can be loaded from png files containing black and white pixels or simple text files
 - some values (like tank speed) can be configured but are fixed at run time
 
diff --git a/tank-frontend/src/App.tsx b/tank-frontend/src/App.tsx
index 6a54b4c..b805877 100644
--- a/tank-frontend/src/App.tsx
+++ b/tank-frontend/src/App.tsx
@@ -1,3 +1,5 @@
+import {useState} from 'react';
+
 import ClientScreen from './ClientScreen';
 import Controls from './Controls.tsx';
 import JoinForm from './JoinForm.tsx';
@@ -7,23 +9,22 @@ import Row from './components/Row.tsx';
 import Scoreboard from './Scoreboard.tsx';
 import Button from './components/Button.tsx';
 import MapChooser from './MapChooser.tsx';
+import {ThemeProvider} from './theme.tsx';
 import './App.css';
-import {ThemeContext, getRandomTheme, useStoredTheme} from './theme.ts';
-import {useState} from 'react';
+import ThemeChooser from './ThemeChooser.tsx';
 
 export default function App() {
-    const [theme, setTheme] = useStoredTheme();
     const [name, setName] = useState<string | null>(null);
 
-    return <ThemeContext.Provider value={theme}>
+    return <ThemeProvider>
         <Column className="flex-grow">
 
             <ClientScreen player={name}/>
 
             <Row>
                 <h1 className="flex-grow">CCCB-Tanks!</h1>
-                <MapChooser />
-                <Button text="☼ change colors" onClick={() => setTheme(_ => getRandomTheme())}/>
+                <MapChooser/>
+                <ThemeChooser/>
                 <Button
                     onClick={() => window.open('https://github.com/kaesaecracker/cccb-tanks-cs', '_blank')?.focus()}
                     text="⌂ source"/>
@@ -40,5 +41,5 @@ export default function App() {
             </Row>
 
         </Column>
-    </ThemeContext.Provider>;
+    </ThemeProvider>;
 }
diff --git a/tank-frontend/src/JoinForm.tsx b/tank-frontend/src/JoinForm.tsx
index 4f4b560..0b5791d 100644
--- a/tank-frontend/src/JoinForm.tsx
+++ b/tank-frontend/src/JoinForm.tsx
@@ -3,7 +3,7 @@ import {useMutation} from '@tanstack/react-query';
 
 import {makeApiUrl} from './serverCalls';
 import Button from './components/Button.tsx';
-import TextInput from './components/TextInput.tsx';
+import {TextInput} from './components/Input.tsx';
 import Dialog from './components/Dialog.tsx';
 import './JoinForm.css';
 
@@ -30,12 +30,11 @@ export default function JoinForm({onDone}: {
 
     const confirm = () => postPlayer.mutate({name});
 
-    return <Dialog className="JoinForm">
-        <h3> Enter your name to play </h3>
+    return <Dialog className="JoinForm" title="Enter your name to play">
         <TextInput
             value={name}
             placeholder="player name"
-            onChange={e => setName(e.target.value)}
+            onChange={n => setName(n)}
             onEnter={confirm}
         />
         <Button
diff --git a/tank-frontend/src/MapChooser.css b/tank-frontend/src/MapChooser.css
index 9bd5c79..600c01b 100644
--- a/tank-frontend/src/MapChooser.css
+++ b/tank-frontend/src/MapChooser.css
@@ -1,15 +1,8 @@
 
-.MapChooser-DropDown {
-    border: solid var(--border-size-thin);
-    padding: var(--padding-normal);
-
-    background: var(--color-background);
-    border-color: var(--color-primary);
-    color: var(--color-primary);
-}
-
 .MapChooser-Row {
-    flex-wrap: wrap;
+    display: grid;
+    width: 100%;
+    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
 }
 
 .MapChooser-Preview {
@@ -21,3 +14,7 @@
 .MapChooser-Preview-Highlight {
     border-color: var(--color-secondary);
 }
+
+.MapChooser-Dialog {
+    width: 100%;
+}
diff --git a/tank-frontend/src/MapChooser.tsx b/tank-frontend/src/MapChooser.tsx
index 4c67eee..1012539 100644
--- a/tank-frontend/src/MapChooser.tsx
+++ b/tank-frontend/src/MapChooser.tsx
@@ -7,6 +7,7 @@ import Column from './components/Column.tsx';
 import Button from './components/Button.tsx';
 import Row from './components/Row.tsx';
 import './MapChooser.css';
+import Spacer from './components/Spacer.tsx';
 
 function base64ToArrayBuffer(base64: string) {
     const binaryString = atob(base64);
@@ -57,8 +58,11 @@ function MapChooserDialog({mapNames, onClose, onConfirm}: {
     readonly onClose: () => void;
 }) {
     const [chosenMap, setChosenMap] = useState<string>();
-    return <Dialog>
-        <h3>Choose a map</h3>
+    return <Dialog
+        className='MapChooser-Dialog'
+        title="Choose a map"
+        onClose={onClose}
+    >
         <Row className="MapChooser-Row overflow-scroll">
             {mapNames.map(name => <MapPreview
                 key={name}
@@ -68,7 +72,7 @@ function MapChooserDialog({mapNames, onClose, onConfirm}: {
             />)}
         </Row>
         <Row>
-            <div className="flex-grow"/>
+            <Spacer/>
             <Button text="« cancel" onClick={onClose}/>
             <Button text="√ confirm" disabled={!chosenMap} onClick={() => chosenMap && onConfirm(chosenMap)}/>
         </Row>
diff --git a/tank-frontend/src/ThemeChooser.css b/tank-frontend/src/ThemeChooser.css
new file mode 100644
index 0000000..a77c83f
--- /dev/null
+++ b/tank-frontend/src/ThemeChooser.css
@@ -0,0 +1,6 @@
+.HslEditor-Inputs {
+    display: grid;
+    column-gap: var(--padding-normal);
+    grid-template-columns: auto auto auto;
+    grid-template-rows: auto;
+}
diff --git a/tank-frontend/src/ThemeChooser.tsx b/tank-frontend/src/ThemeChooser.tsx
new file mode 100644
index 0000000..acfc9e2
--- /dev/null
+++ b/tank-frontend/src/ThemeChooser.tsx
@@ -0,0 +1,115 @@
+import Button from './components/Button.tsx';
+import {getRandomTheme, HSL, hslToString, useHslTheme} from './theme.tsx';
+import Dialog from './components/Dialog.tsx';
+import {useMemo, useState} from 'react';
+import {NumberInput, RangeInput, TextInput} from './components/Input.tsx';
+import Row from './components/Row.tsx';
+import Column from './components/Column.tsx';
+import './ThemeChooser.css';
+import Spacer from './components/Spacer.tsx';
+
+function HslEditor({name, value, setValue}: {
+    name: string;
+    value: HSL;
+    setValue: (value: HSL) => void
+}) {
+    const setH = (h: number) => setValue({...value, h});
+    const setS = (s: number) => setValue({...value, s});
+    const setL = (l: number) => setValue({...value, l});
+
+    return <Column>
+        <Row>
+            <div className="" style={{background: hslToString(value), border: '1px solid white', aspectRatio: '1'}}/>
+            <p>{name}</p>
+        </Row>
+        <div className="HslEditor-Inputs">
+            <p>Hue</p>
+            <NumberInput value={Math.round(value.h)} onChange={setH}/>
+            <RangeInput value={Math.round(value.h)} min={0} max={360} onChange={setH}/>
+
+            <p>Saturation</p>
+            <NumberInput value={Math.round(value.s)} onChange={setS}/>
+            <RangeInput value={Math.round(value.s)} min={0} max={100} onChange={setS}/>
+
+            <p>Lightness</p>
+            <NumberInput value={Math.round(value.l)} onChange={setL}/>
+            <RangeInput value={Math.round(value.l)} min={0} max={100} onChange={setL}/>
+        </div>
+    </Column>;
+}
+
+function ThemeChooserDialog({onClose}: {
+    onClose: () => void;
+}) {
+    const {hslTheme, setHslTheme} = useHslTheme();
+    const [themeString, setThemeString] = useState<string>(JSON.stringify(hslTheme));
+    const [errorMsg, setErrorMsg] = useState<string>();
+
+    useMemo(() => {
+        setThemeString(JSON.stringify(hslTheme));
+    }, [hslTheme]);
+
+    return <Dialog title="Theme editor" onClose={onClose}>
+        <Row>
+            <Button
+                text="? randomize"
+                onClick={() => setHslTheme(_ => getRandomTheme())}/>
+            <Spacer/>
+        </Row>
+        <Row>
+            <TextInput
+                value={themeString}
+                onChange={setThemeString}
+                className="flex-grow"/>
+            <Button text="» import" onClick={() => {
+                try {
+                    const theme = JSON.parse(themeString);
+                    setHslTheme(old => ({...old, theme}));
+                } catch (e: any) {
+                    setErrorMsg(e.message);
+                }
+            }}/>
+            {errorMsg &&
+                <Dialog
+                    title="Error"
+                    onClose={() => setErrorMsg(undefined)}
+                >
+                    <p>{errorMsg}</p>
+                </Dialog>
+            }
+        </Row>
+        <Column className="overflow-scroll">
+            <HslEditor
+                name="background"
+                value={hslTheme.background}
+                setValue={value => setHslTheme(old => ({...old, background: value}))}/>
+            <HslEditor
+                name="primary"
+                value={hslTheme.primary}
+                setValue={value => setHslTheme(old => ({...old, primary: value}))}/>
+            <HslEditor
+                name="secondary"
+                value={hslTheme.secondary}
+                setValue={value => setHslTheme(old => ({...old, secondary: value}))}/>
+            <HslEditor
+                name="tertiary"
+                value={hslTheme.tertiary}
+                setValue={value => setHslTheme(old => ({...old, tertiary: value}))}/>
+            <HslEditor
+                name="text"
+                value={hslTheme.text}
+                setValue={value => setHslTheme(old => ({...old, text: value}))}/>
+        </Column>
+    </Dialog>;
+}
+
+export default function ThemeChooser({}: {}) {
+    const [open, setOpen] = useState(false);
+
+    return <>
+        <Button
+            text="☼ change colors"
+            onClick={() => setOpen(true)}/>
+        {open && <ThemeChooserDialog onClose={() => setOpen(false)}/>}
+    </>;
+}
diff --git a/tank-frontend/src/components/Dialog.tsx b/tank-frontend/src/components/Dialog.tsx
index 07ff787..86130ad 100644
--- a/tank-frontend/src/components/Dialog.tsx
+++ b/tank-frontend/src/components/Dialog.tsx
@@ -1,12 +1,22 @@
 import {ReactNode} from 'react';
 import Column from './Column.tsx';
+import Row from './Row.tsx';
+import Button from './Button.tsx';
 import './Dialog.css';
 
-export default function Dialog({children, className}: {
-    children: ReactNode;
+export default function Dialog({children, className, title, onClose}: {
+    title?: string;
+    children?: ReactNode;
     className?: string;
+    onClose?: () => void;
 }) {
-    return <Column className={'Dialog overflow-scroll ' + (className ?? '')}>
-        {children}
-    </Column>
+    return <Column className={'Dialog ' + (className ?? '')}>
+        <Row>
+            <h3 className="flex-grow">{title}</h3>
+            {onClose && <Button text="x" onClick={onClose}/>}
+        </Row>
+        <Column className='overflow-scroll'>
+            {children}
+        </Column>
+    </Column>;
 }
diff --git a/tank-frontend/src/components/Input.css b/tank-frontend/src/components/Input.css
new file mode 100644
index 0000000..d2a505b
--- /dev/null
+++ b/tank-frontend/src/components/Input.css
@@ -0,0 +1,9 @@
+.Input {
+    background-color: var(--color-background);
+    color: var(--color-text);
+    padding: var(--padding-normal);
+}
+
+.RangeInput {
+    appearance: auto;
+}
diff --git a/tank-frontend/src/components/Input.tsx b/tank-frontend/src/components/Input.tsx
new file mode 100644
index 0000000..37f7ab7
--- /dev/null
+++ b/tank-frontend/src/components/Input.tsx
@@ -0,0 +1,80 @@
+import './Input.css';
+
+export function TextInput({onChange, className, value, placeholder, onEnter}: {
+    onChange?: (value: string) => void;
+    className?: string;
+    value: string;
+    placeholder?: string;
+    onEnter?: () => void;
+}) {
+    return <input
+        type="text"
+        className={'Input ' + (className ?? '')}
+        value={value}
+        placeholder={placeholder}
+        onChange={event => {
+            if (!onChange)
+                return;
+            onChange(event.target.value);
+        }}
+        onKeyUp={event => {
+            if (!onEnter || event.key !== 'Enter')
+                return;
+            onEnter();
+        }}
+    />;
+}
+
+export function NumberInput({onChange, className, value, placeholder, onEnter}: {
+    onChange?: (value: number) => void;
+    className?: string;
+    value: number;
+    placeholder?: string;
+    onEnter?: () => void;
+}) {
+    return <input
+        type="number"
+        className={'Input ' + (className ?? '')}
+        value={value}
+        placeholder={placeholder}
+        onChange={event => {
+            if (!onChange)
+                return;
+            onChange(parseFloat(event.target.value));
+        }}
+        onKeyUp={event => {
+            if (!onEnter || event.key !== 'Enter')
+                return;
+            onEnter();
+        }}
+    />;
+}
+
+export function RangeInput({onChange, className, value, placeholder, onEnter, min, max}: {
+    onChange?: (value: number) => void;
+    className?: string;
+    value: number;
+    min: number;
+    max: number;
+    placeholder?: string;
+    onEnter?: () => void;
+}) {
+    return <input
+        type="range"
+        className={'Input RangeInput ' + (className ?? '')}
+        value={value} min={min} max={max}
+        placeholder={placeholder}
+        onChange={event => {
+            if (!onChange)
+                return;
+            onChange(parseFloat(event.target.value));
+        }}
+        onKeyUp={event => {
+            if (!onEnter || event.key !== 'Enter')
+                return;
+            onEnter();
+        }}
+    />;
+}
+
+
diff --git a/tank-frontend/src/components/PixelGridCanvas.tsx b/tank-frontend/src/components/PixelGridCanvas.tsx
index fc90f98..cf8eb68 100644
--- a/tank-frontend/src/components/PixelGridCanvas.tsx
+++ b/tank-frontend/src/components/PixelGridCanvas.tsx
@@ -1,6 +1,6 @@
-import {hslToString, ThemeContext} from '../theme.ts';
-import {useContext, useEffect, useRef} from 'react';
+import {useEffect, useRef} from 'react';
 import './PixelGridCanvas.css';
+import {useRgbaTheme} from '../theme.tsx';
 
 const pixelsPerRow = 352;
 const pixelsPerCol = 160;
@@ -20,12 +20,6 @@ function getPixelDataIndexes(bitIndex: number) {
     };
 }
 
-function normalizeColor(context: CanvasRenderingContext2D, color: string) {
-    context.fillStyle = color;
-    context.fillRect(0, 0, 1, 1);
-    return context.getImageData(0, 0, 1, 1).data;
-}
-
 function parseAdditionalDataNibble(nibble: number) {
     const isPlayerMask = 1;
     const entityTypeMask = 12;
@@ -107,7 +101,7 @@ function drawPixelsToCanvas(
 export default function PixelGridCanvas({pixels}: {
     readonly pixels: Uint8ClampedArray;
 }) {
-    const theme = useContext(ThemeContext);
+    const theme = useRgbaTheme();
     const canvasRef = useRef<HTMLCanvasElement>(null);
 
     useEffect(() => {
@@ -137,12 +131,12 @@ export default function PixelGridCanvas({pixels}: {
                 pixels,
                 additional: additionalData,
                 colors: {
-                    background: normalizeColor(drawContext, hslToString(theme.background)),
-                    foreground: normalizeColor(drawContext, hslToString(theme.primary)),
-                    player: normalizeColor(drawContext, hslToString(theme.secondary)),
-                    tanks: normalizeColor(drawContext, hslToString(theme.tertiary)),
-                    powerUps: normalizeColor(drawContext, hslToString(theme.tertiary)),
-                    bullets: normalizeColor(drawContext, hslToString(theme.tertiary))
+                    background: theme.background,
+                    foreground: theme.primary,
+                    player: theme.secondary,
+                    tanks: theme.tertiary,
+                    powerUps: theme.tertiary,
+                    bullets: theme.tertiary
                 }
             });
         };
diff --git a/tank-frontend/src/components/Row.tsx b/tank-frontend/src/components/Row.tsx
index 41d542c..c31b988 100644
--- a/tank-frontend/src/components/Row.tsx
+++ b/tank-frontend/src/components/Row.tsx
@@ -1,9 +1,12 @@
-import {ReactNode} from "react";
+import {ReactNode} from 'react';
 
 import './Row.css';
 
-export default function Row({children, className}: { children: ReactNode, className?: string }) {
+export default function Row({children, className}: {
+    children?: ReactNode;
+    className?: string;
+}) {
     return <div className={'Row flex-row ' + (className ?? '')}>
         {children}
-    </div>
+    </div>;
 }
diff --git a/tank-frontend/src/components/Spacer.tsx b/tank-frontend/src/components/Spacer.tsx
new file mode 100644
index 0000000..a2f41d1
--- /dev/null
+++ b/tank-frontend/src/components/Spacer.tsx
@@ -0,0 +1,4 @@
+
+export default function Spacer() {
+    return <div className='flex-grow' />;
+}
diff --git a/tank-frontend/src/components/TextInput.css b/tank-frontend/src/components/TextInput.css
deleted file mode 100644
index df3f377..0000000
--- a/tank-frontend/src/components/TextInput.css
+++ /dev/null
@@ -1,3 +0,0 @@
-.TextInput {
-    padding: var(--padding-normal);
-}
diff --git a/tank-frontend/src/components/TextInput.tsx b/tank-frontend/src/components/TextInput.tsx
deleted file mode 100644
index b806045..0000000
--- a/tank-frontend/src/components/TextInput.tsx
+++ /dev/null
@@ -1,21 +0,0 @@
-import {ChangeEventHandler} from "react";
-import './TextInput.css';
-
-export default function TextInput(props: {
-    onChange?: ChangeEventHandler<HTMLInputElement> | undefined;
-    className?: string;
-    value: string;
-    placeholder: string;
-    onEnter?: () => void;
-}) {
-    return <input
-        {...props}
-        type="text"
-        className={'TextInput ' + (props.className?? '')}
-
-        onKeyUp={event => {
-            if (props.onEnter && event.key === 'Enter')
-                props.onEnter();
-        }}
-    />;
-}
diff --git a/tank-frontend/src/theme.ts b/tank-frontend/src/theme.ts
deleted file mode 100644
index 903c05d..0000000
--- a/tank-frontend/src/theme.ts
+++ /dev/null
@@ -1,93 +0,0 @@
-import {useStoredObjectState} from './useStoredState.ts';
-import {createContext} from 'react';
-
-export type Theme = {
-    primary: HSL;
-    secondary: HSL;
-    background: HSL;
-    tertiary: HSL;
-}
-
-// @ts-ignore
-const rootStyle = document.querySelector(':root')?.style;
-
-function getRandom(min: number, max: number) {
-    return min + Math.random() * (max - min);
-}
-
-type HSL = {
-    h: number;
-    s: number;
-    l: number;
-}
-
-function getRandomHsl(params: {
-    minHue?: number,
-    maxHue?: number,
-    minSaturation?: number,
-    maxSaturation?: number,
-    minLightness?: number,
-    maxLightness?: number,
-}): HSL {
-    const values = {
-        minHue: 0,
-        maxHue: 360,
-        minSaturation: 0,
-        maxSaturation: 100,
-        minLightness: 0,
-        maxLightness: 100,
-        ...params
-    };
-    const h = getRandom(values.minHue, values.maxHue);
-    const s = getRandom(values.minSaturation, values.maxSaturation);
-    const l = getRandom(values.minLightness, values.maxLightness);
-    return {h, s, l};
-}
-
-export function hslToString({h, s, l}: HSL) {
-    return `hsl(${h},${s}%,${l}%)`;
-}
-
-function angle(a: number) {
-    return ((a % 360.0) + 360) % 360;
-}
-
-export function getRandomTheme(): Theme {
-    const goldenAngle = 180 * (3 - Math.sqrt(5));
-
-    const background = getRandomHsl({maxSaturation: 50, minLightness: 10, maxLightness: 30});
-
-    const otherColorParams = {
-        minSaturation: background.s,
-        maxSaturation: 90,
-        minLightness: background.l + 20,
-        maxLightness: 90
-    };
-
-    const primary = getRandomHsl(otherColorParams);
-    primary.h = angle(-1 * goldenAngle + primary.h);
-
-    const secondary = getRandomHsl(otherColorParams);
-    primary.h = angle(+1 * goldenAngle + primary.h);
-
-    const tertiary = getRandomHsl(otherColorParams);
-    primary.h = angle(+3 * goldenAngle + primary.h);
-
-    return {background, primary, secondary, tertiary};
-}
-
-function applyTheme(theme: Theme) {
-    console.log('apply theme', theme);
-    rootStyle.setProperty('--color-primary', hslToString(theme.primary));
-    rootStyle.setProperty('--color-secondary', hslToString(theme.secondary));
-    rootStyle.setProperty('--color-background', hslToString(theme.background));
-}
-
-export function useStoredTheme() {
-    return useStoredObjectState<Theme>('theme', getRandomTheme, {
-        load: applyTheme,
-        save: applyTheme
-    });
-}
-
-export const ThemeContext = createContext<Theme>(getRandomTheme());
diff --git a/tank-frontend/src/theme.tsx b/tank-frontend/src/theme.tsx
new file mode 100644
index 0000000..2315e02
--- /dev/null
+++ b/tank-frontend/src/theme.tsx
@@ -0,0 +1,169 @@
+import {useStoredObjectState} from './useStoredState.ts';
+import {createContext, ReactNode, useContext, useMemo, useRef, useState} from 'react';
+
+export type HSL = {
+    h: number;
+    s: number;
+    l: number;
+}
+
+export type HslTheme = {
+    primary: HSL;
+    secondary: HSL;
+    background: HSL;
+    tertiary: HSL;
+    text: HSL;
+}
+
+type Rgba = Uint8ClampedArray;
+
+export type RgbaTheme = {
+    primary: Rgba;
+    secondary: Rgba;
+    background: Rgba;
+    tertiary: Rgba;
+}
+
+// @ts-ignore
+const rootStyle = document.querySelector(':root')?.style;
+
+function getRandom(min: number, max: number) {
+    return min + Math.random() * (max - min);
+}
+
+function getRandomHsl(params: {
+    minHue?: number,
+    maxHue?: number,
+    minSaturation?: number,
+    maxSaturation?: number,
+    minLightness?: number,
+    maxLightness?: number,
+}): HSL {
+    const values = {
+        minHue: 0,
+        maxHue: 360,
+        minSaturation: 0,
+        maxSaturation: 100,
+        minLightness: 0,
+        maxLightness: 100,
+        ...params
+    };
+    const h = getRandom(values.minHue, values.maxHue);
+    const s = getRandom(values.minSaturation, values.maxSaturation);
+    const l = getRandom(values.minLightness, values.maxLightness);
+    return {h, s, l};
+}
+
+export function hslToString({h, s, l}: HSL) {
+    return `hsl(${h},${s}%,${l}%)`;
+}
+
+function angle(a: number) {
+    return ((a % 360.0) + 360) % 360;
+}
+
+export function getRandomTheme(): HslTheme {
+    const goldenAngle = 180 * (3 - Math.sqrt(5));
+
+    const background = getRandomHsl({maxSaturation: 50, minLightness: 10, maxLightness: 30});
+
+    const otherColorParams = {
+        minSaturation: background.s,
+        maxSaturation: 90,
+        minLightness: background.l + 20,
+        maxLightness: 90
+    };
+
+    const primary = getRandomHsl(otherColorParams);
+    primary.h = angle(-1 * goldenAngle + primary.h);
+
+    const secondary = getRandomHsl(otherColorParams);
+    primary.h = angle(+1 * goldenAngle + primary.h);
+
+    const tertiary = getRandomHsl(otherColorParams);
+    primary.h = angle(+3 * goldenAngle + primary.h);
+
+    const text = {h: 0, s: 0, l: 100};
+
+    return {background, primary, secondary, tertiary, text};
+}
+
+const dummyRgbaTheme: RgbaTheme = {
+    primary: new Uint8ClampedArray([0, 0, 0, 0]),
+    secondary: new Uint8ClampedArray([0, 0, 0, 0]),
+    background: new Uint8ClampedArray([0, 0, 0, 0]),
+    tertiary: new Uint8ClampedArray([0, 0, 0, 0])
+};
+
+function hslToRgba(context: CanvasRenderingContext2D, color: HSL) {
+    context.fillStyle = hslToString(color);
+    context.fillRect(0, 0, 1, 1);
+    return context.getImageData(0, 0, 1, 1).data;
+}
+
+const HslThemeContext = createContext<null | {
+    hslTheme: HslTheme,
+    setHslTheme: (mutator: (oldState: HslTheme) => HslTheme) => void
+}>(null);
+const RgbaThemeContext = createContext<RgbaTheme>(dummyRgbaTheme);
+
+export function useRgbaTheme() {
+    return useContext(RgbaThemeContext);
+}
+
+export function useHslTheme() {
+    const context = useContext(HslThemeContext);
+    if (context === null) {
+        throw new Error();
+    }
+
+    return context;
+}
+
+export function ThemeProvider({children}: {
+    children?: ReactNode;
+}) {
+    const [rgbaTheme, setRgbaTheme] = useState<RgbaTheme | null>(null);
+
+    function applyTheme(theme: HslTheme) {
+        console.log('apply theme', theme);
+        rootStyle.setProperty('--color-primary', hslToString(theme.primary));
+        rootStyle.setProperty('--color-secondary', hslToString(theme.secondary));
+        rootStyle.setProperty('--color-background', hslToString(theme.background));
+        rootStyle.setProperty('--color-text', hslToString(theme.text));
+    }
+
+    const [hslTheme, setHslTheme] = useStoredObjectState<HslTheme>('theme2', getRandomTheme, {
+        load: applyTheme,
+        save: applyTheme
+    });
+    const canvasRef = useRef<HTMLCanvasElement>(null);
+
+    const canvas = canvasRef.current;
+
+    useMemo(() => {
+        if (!canvas)
+            return;
+
+        const drawContext = canvas.getContext('2d', {
+            alpha: false,
+            colorSpace: 'srgb',
+            willReadFrequently: true
+        });
+        if (!drawContext)
+            throw new Error('could not get draw context');
+        setRgbaTheme({
+            background: hslToRgba(drawContext, hslTheme.background),
+            primary: hslToRgba(drawContext, hslTheme.primary),
+            secondary: hslToRgba(drawContext, hslTheme.secondary),
+            tertiary: hslToRgba(drawContext, hslTheme.tertiary),
+        });
+    }, [hslTheme, canvas]);
+
+    return <HslThemeContext.Provider value={{hslTheme, setHslTheme}}>
+        <RgbaThemeContext.Provider value={rgbaTheme || dummyRgbaTheme}>
+            <canvas hidden={true} ref={canvasRef} width={1} height={1}/>
+            {children}
+        </RgbaThemeContext.Provider>;
+    </HslThemeContext.Provider>;
+}
diff --git a/tanks-backend/TanksServer/Endpoints.cs b/tanks-backend/TanksServer/Endpoints.cs
index 0eb0100..e0e0252 100644
--- a/tanks-backend/TanksServer/Endpoints.cs
+++ b/tanks-backend/TanksServer/Endpoints.cs
@@ -1,7 +1,12 @@
+using System.IO;
+using System.Text;
+using System.Text.Json;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Diagnostics.HealthChecks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.HttpResults;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
 using TanksServer.GameLogic;
 using TanksServer.Interactivity;
 
@@ -25,6 +30,11 @@ internal sealed class Endpoints(
         app.MapGet("/map", () => mapService.MapNames);
         app.MapPost("/map", PostMap);
         app.MapGet("/map/{name}", GetMapByName);
+
+        app.MapHealthChecks("/health", new HealthCheckOptions
+        {
+            ResponseWriter = WriteJsonHealthCheckResponse
+        });
     }
 
     private Results<BadRequest<string>, NotFound<string>, Ok> PostMap([FromQuery] string name)
@@ -107,4 +117,41 @@ internal sealed class Endpoints(
         var mapInfo = new MapInfo(prototype.Name, prototype.GetType().Name, preview.Data);
         return TypedResults.Ok(mapInfo);
     }
+
+    private static Task WriteJsonHealthCheckResponse(HttpContext context, HealthReport healthReport)
+    {
+        context.Response.ContentType = "application/json; charset=utf-8";
+
+        var options = new JsonWriterOptions { Indented = true };
+
+        using var memoryStream = new MemoryStream();
+        using (var jsonWriter = new Utf8JsonWriter(memoryStream, options))
+        {
+            jsonWriter.WriteStartObject();
+            jsonWriter.WriteString("status", healthReport.Status.ToString());
+            jsonWriter.WriteStartObject("results");
+
+            foreach (var healthReportEntry in healthReport.Entries)
+            {
+                jsonWriter.WriteStartObject(healthReportEntry.Key);
+                jsonWriter.WriteString("status",
+                    healthReportEntry.Value.Status.ToString());
+                jsonWriter.WriteString("description",
+                    healthReportEntry.Value.Description);
+                jsonWriter.WriteStartObject("data");
+
+                foreach (var item in healthReportEntry.Value.Data)
+                    jsonWriter.WriteString(item.Key, item.Value.ToString());
+
+                jsonWriter.WriteEndObject();
+                jsonWriter.WriteEndObject();
+            }
+
+            jsonWriter.WriteEndObject();
+            jsonWriter.WriteEndObject();
+        }
+
+        return context.Response.WriteAsync(
+            Encoding.UTF8.GetString(memoryStream.ToArray()));
+    }
 }
diff --git a/tanks-backend/TanksServer/GameLogic/MapService.cs b/tanks-backend/TanksServer/GameLogic/MapService.cs
index b9263f4..28a5aef 100644
--- a/tanks-backend/TanksServer/GameLogic/MapService.cs
+++ b/tanks-backend/TanksServer/GameLogic/MapService.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using DisplayCommands;
@@ -13,8 +14,8 @@ internal sealed class MapService
     public const ushort PixelsPerRow = TilesPerRow * TileSize;
     public const ushort PixelsPerColumn = TilesPerColumn * TileSize;
 
-    private readonly Dictionary<string, MapPrototype> _mapPrototypes = new();
-    private readonly Dictionary<string, PixelGrid> _mapPreviews = new();
+    private readonly ConcurrentDictionary<string, MapPrototype> _mapPrototypes = new();
+    private readonly ConcurrentDictionary<string, PixelGrid> _mapPreviews = new();
 
     public IEnumerable<string> MapNames => _mapPrototypes.Keys;
 
@@ -52,7 +53,8 @@ internal sealed class MapService
     {
         var name = MapNameFromFilePath(file);
         var prototype = new SpriteMapPrototype(name, Sprite.FromImageFile(file));
-        _mapPrototypes.Add(name, prototype);
+        var added = _mapPrototypes.TryAdd(name, prototype);
+        Debug.Assert(added);
     }
 
     private void LoadMapString(string file)
@@ -60,7 +62,7 @@ internal sealed class MapService
         var name = MapNameFromFilePath(file);
         var map = File.ReadAllText(file).ReplaceLineEndings(string.Empty).Trim();
         var prototype = new TextMapPrototype(name, map);
-        _mapPrototypes.Add(name, prototype);
+        _mapPrototypes.TryAdd(name, prototype);
     }
 
     private static string MapNameFromFilePath(string filePath) => Path.GetFileName(filePath).ToUpperInvariant();
diff --git a/tanks-backend/TanksServer/GameLogic/UpdatesPerSecondCounter.cs b/tanks-backend/TanksServer/GameLogic/UpdatesPerSecondCounter.cs
index 71a9818..f2a2613 100644
--- a/tanks-backend/TanksServer/GameLogic/UpdatesPerSecondCounter.cs
+++ b/tanks-backend/TanksServer/GameLogic/UpdatesPerSecondCounter.cs
@@ -1,13 +1,42 @@
 using System.Diagnostics;
+using System.Globalization;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
 
 namespace TanksServer.GameLogic;
 
-internal sealed class UpdatesPerSecondCounter(ILogger<UpdatesPerSecondCounter> logger) : ITickStep
+internal sealed class UpdatesPerSecondCounter(
+    ILogger<UpdatesPerSecondCounter> logger
+) : ITickStep, IHealthCheck
 {
     private static readonly TimeSpan LongTime = TimeSpan.FromSeconds(5);
     private static readonly TimeSpan CriticalUpdateTime = TimeSpan.FromMilliseconds(50);
 
     private readonly Stopwatch _long = Stopwatch.StartNew();
+
+    private readonly record struct Statistics(
+        ulong Updates,
+        TimeSpan TotalTime,
+        double AverageUpdatesPerSecond,
+        TimeSpan MinFrameTime,
+        TimeSpan AverageFrameTime,
+        TimeSpan MaxFrameTime)
+    {
+        public override string ToString() =>
+            $"{nameof(Updates)}: {Updates}, {nameof(TotalTime)}: {TotalTime}, {nameof(AverageUpdatesPerSecond)}: {AverageUpdatesPerSecond}, {nameof(MinFrameTime)}: {MinFrameTime}, {nameof(AverageFrameTime)}: {AverageFrameTime}, {nameof(MaxFrameTime)}: {MaxFrameTime}";
+
+        public Dictionary<string, object> ToDictionary() => new()
+        {
+            [nameof(Updates)] = Updates.ToString(),
+            [nameof(TotalTime)] = TotalTime.ToString(),
+            [nameof(AverageUpdatesPerSecond)] = AverageUpdatesPerSecond.ToString(CultureInfo.InvariantCulture),
+            [nameof(MinFrameTime)] = MinFrameTime.ToString(),
+            [nameof(AverageFrameTime)] = AverageFrameTime.ToString(),
+            [nameof(MaxFrameTime)] = MaxFrameTime.ToString()
+        };
+    };
+
+    private Statistics? _currentStatistics = null;
+
     private ulong _updatesSinceLongReset;
     private TimeSpan _minFrameTime = TimeSpan.MaxValue;
     private TimeSpan _maxFrameTime = TimeSpan.MinValue;
@@ -40,16 +69,20 @@ internal sealed class UpdatesPerSecondCounter(ILogger<UpdatesPerSecondCounter> l
 
     private void LogCounters()
     {
+        var time = _long.Elapsed;
+
+        _currentStatistics = new Statistics(
+            _updatesSinceLongReset,
+            time,
+            _updatesSinceLongReset / time.TotalSeconds,
+            _minFrameTime,
+            time / _updatesSinceLongReset,
+            _maxFrameTime);
+
         if (!logger.IsEnabled(LogLevel.Debug))
             return;
 
-        var time = _long.Elapsed;
-        var averageTime = Math.Round(time.TotalMilliseconds / _updatesSinceLongReset, 2);
-        var averageUps = Math.Round(_updatesSinceLongReset / time.TotalSeconds, 2);
-        var min = Math.Round(_minFrameTime.TotalMilliseconds, 2);
-        var max = Math.Round(_maxFrameTime.TotalMilliseconds, 2);
-        logger.LogDebug("count={}, time={}, avg={}ms, ups={}, min={}ms, max={}ms",
-            _updatesSinceLongReset, time, averageTime, averageUps, min, max);
+        logger.LogDebug("statistics: {}", _currentStatistics);
     }
 
     private void ResetCounters()
@@ -59,4 +92,23 @@ internal sealed class UpdatesPerSecondCounter(ILogger<UpdatesPerSecondCounter> l
         _minFrameTime = TimeSpan.MaxValue;
         _maxFrameTime = TimeSpan.MinValue;
     }
+
+    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context,
+        CancellationToken cancellationToken = new())
+    {
+        var stats = _currentStatistics;
+        if (stats == null)
+        {
+            return Task.FromResult(
+                HealthCheckResult.Degraded("no statistics available yet - this is expected shortly after start"));
+        }
+
+        if (stats.Value.MaxFrameTime > CriticalUpdateTime)
+        {
+            return Task.FromResult(HealthCheckResult.Degraded("max frame time too high", null,
+                stats.Value.ToDictionary()));
+        }
+
+        return Task.FromResult(HealthCheckResult.Healthy("", stats.Value.ToDictionary()));
+    }
 }
diff --git a/tanks-backend/TanksServer/Program.cs b/tanks-backend/TanksServer/Program.cs
index 40263f2..91c14fe 100644
--- a/tanks-backend/TanksServer/Program.cs
+++ b/tanks-backend/TanksServer/Program.cs
@@ -51,6 +51,9 @@ public static class Program
 
         builder.Services.AddHttpLogging(_ => { });
 
+        var healthCheckBuilder = builder.Services.AddHealthChecks();
+        healthCheckBuilder.AddCheck<UpdatesPerSecondCounter>("updates check");
+
         builder.Services.Configure<HostConfiguration>(builder.Configuration.GetSection("Host"));
         var hostConfiguration = builder.Configuration.GetSection("Host").Get<HostConfiguration>();
         if (hostConfiguration == null)
@@ -66,12 +69,14 @@ public static class Program
         builder.Services.AddSingleton<BufferPool>();
         builder.Services.AddSingleton<EmptyTileFinder>();
         builder.Services.AddSingleton<ChangeToRequestedMap>();
+        builder.Services.AddSingleton<UpdatesPerSecondCounter>();
 
         builder.Services.AddHostedService<GameTickWorker>();
         builder.Services.AddHostedService(sp => sp.GetRequiredService<ControlsServer>());
         builder.Services.AddHostedService(sp => sp.GetRequiredService<ClientScreenServer>());
 
-        builder.Services.AddSingleton<ITickStep, ChangeToRequestedMap>(sp => sp.GetRequiredService<ChangeToRequestedMap>());
+        builder.Services.AddSingleton<ITickStep, ChangeToRequestedMap>(sp =>
+            sp.GetRequiredService<ChangeToRequestedMap>());
         builder.Services.AddSingleton<ITickStep, MoveBullets>();
         builder.Services.AddSingleton<ITickStep, CollideBullets>();
         builder.Services.AddSingleton<ITickStep, RotateTanks>();
@@ -82,7 +87,8 @@ public static class Program
         builder.Services.AddSingleton<ITickStep, SpawnPowerUp>();
         builder.Services.AddSingleton<ITickStep, GeneratePixelsTickStep>();
         builder.Services.AddSingleton<ITickStep, PlayerServer>(sp => sp.GetRequiredService<PlayerServer>());
-        builder.Services.AddSingleton<ITickStep, UpdatesPerSecondCounter>();
+        builder.Services.AddSingleton<ITickStep, UpdatesPerSecondCounter>(sp =>
+            sp.GetRequiredService<UpdatesPerSecondCounter>());
 
         builder.Services.AddSingleton<IDrawStep, DrawMapStep>();
         builder.Services.AddSingleton<IDrawStep, DrawPowerUpsStep>();
diff --git a/tanks-backend/TanksServer/assets/maps/test2.png b/tanks-backend/TanksServer/assets/maps/template.png
similarity index 100%
rename from tanks-backend/TanksServer/assets/maps/test2.png
rename to tanks-backend/TanksServer/assets/maps/template.png
diff --git a/tanks-backend/TanksServer/assets/maps/template.txt b/tanks-backend/TanksServer/assets/maps/template.txt
new file mode 100644
index 0000000..5841c00
--- /dev/null
+++ b/tanks-backend/TanksServer/assets/maps/template.txt
@@ -0,0 +1,20 @@
+############################################
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+#..........................................#
+############################################