IsaacRecomp

The Binding of Isaac (Flash), rebuilt as a native program.
No Flash Player, no emulator: the same game you know, at 60 fps and in high resolution,
on PC, Android and Nintendo Switch.

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😢 What is this?

The Binding of Isaac came out in 2011 as a Flash game. Flash is gone, and the Steam version still relies on an old player that runs at 30 fps, in a small window, with the performance limits of its time.

This project translates all of the game's original code into C++ and runs it on a modern, native engine written from scratch. Graphics, sounds and music are read from your own Steam Isaac.exe at startup, so you need the original game. What changes is how it runs, and where:

	Original Flash	Recomp
Frame rate	30 fps	60 fps (or whatever your display does: 120, 144…)
Resolution	800×600, upscaled	Native (1080p, 1440p, 4K…)
Game logic	30 Hz	Exactly 30 Hz: same physics and patterns, checked frame by frame against the original
Performance	Can stutter with many enemies	Smooth, with drawing spread across CPU cores
Controllers	Needed JoyToKey	Supported out of the box, with analog movement
Versions	One per install	Original, Wrath of the Lamb and Eternal Edition in one program
Platforms	Windows / Mac	Windows, Linux, Android and Nintendo Switch (homebrew)

📥 Downloads

Everything is on the Releases page. Pick the package for your device:

Platform	File	Guide
Windows (64-bit)	IsaacRecomp_Win64.zip	Installation (PC)
Linux (64-bit)	IsaacRecomp_Linux64.tar.gz	Installation (PC)
Android (phone or tablet)	IsaacRecomp.apk	Android
Nintendo Switch	IsaacRecomp_Switch.zip	Nintendo Switch

On every platform you also need the game's Isaac.exe from your Steam copy (see Get the original game).

🕹️ Comparisons

30 fps → 60 fps

The logic still runs at 30 ticks per second, just like the original, so the game feels exactly the same. Every in-between frame is drawn by interpolating between the last two ticks: movement, animations, fades and room transitions all play at your display's refresh rate.

_{Shown in slow motion (×0.5) so the difference is visible on any screen. Real-time 60 fps video.}

Real high resolution

Vector art is rasterized at your screen's actual resolution, and the layers the game used to paint at 640×480 (floor, blood, shadows, minimap) are generated at 1440×1080.

All three Steam versions

If you have more than one version of the game, the program recognizes each one by its content and lets you pick at startup. Each version keeps its own save file.

✨ What's new compared to the original

• 60 fps or more, with the game logic untouched at 30 Hz.
• Native 1080p / 4K, with no thin white seams between colored areas (shapes are rasterized the way Flash does it).
• No pop-in: graphics are prepared in the background while the opening cutscene plays.
• Smooth room transitions, with no sudden jumps after a hiccup.
• Controller support without external tools. Every menu works with the controller alone: the selected option is highlighted in pink, A/✕ presses it and B/◯ goes back.
• Control rebinding inside the game (Options → Controls → Rebind controls) for keyboard, controller and touch.
• Analog movement: with a stick, Isaac's speed follows how far you push it, like in Rebirth (it can be turned off).
• Touch controls on Android and on Switch in handheld mode: floating joysticks, tappable HUD and a pause button.
• Low input latency: input keeps being read while the program waits for the display.
• Cleaned-up options menu: options that depended on Flash and no longer do anything are gone.
• Fullscreen or windowed (F11 or Alt+Enter), fitted to your desktop's usable area.
• Built-in performance overlay (F3).
• Original, Wrath of the Lamb and Eternal Edition in a single program.
• Save converter to bring your progress from the Flash version (and back).

📦 Installation (PC)

1. Get the original game

Buy The Binding of Isaac on Steam (and Wrath of the Lamb if you want the expansion). Install it and open its folder: in Steam, right-click the game → Manage → Browse local files.

There are two executables in there:

File	What it is
Isaac.exe	The game itself: it contains all of its graphics, sounds and code. This is the one you need.
Binding_of_Isaac.exe	Just the Steam launcher. Not useful here.

2. Download the recomp

Go to Releases and grab the package for your system:

• Windows (64-bit): IsaacRecomp_Win64.zip
• Linux (64-bit): IsaacRecomp_Linux64.tar.gz

3. Put them together and play

1. Extract the recomp anywhere you like.
2. Copy Isaac.exe from Steam next to IsaacRecomp.exe (on Linux, next to isaac).
3. Run IsaacRecomp.exe (on Linux: ./isaac).

Requirements: 64-bit Windows or Linux, and a graphics card that supports OpenGL 3.3.

💾 Bringing your Flash saves over

Every package includes tools/save_converter.html: open it in any web browser (it works offline, nothing is uploaded). It turns the Flash game's so.sol into the IsaacRecomp save file and back, for the original game, Wrath of the Lamb and Eternal Edition. Stats, items, secrets, bosses and unlock order carry over. Close the game and back up your save before replacing it. The converter was originally made by g333nza.

🎮 PC controls

The original controls, plus controller support. Controller buttons adapt to whether you are playing, paused or in a menu:

Action	Keyboard	Controller (in game)	Controller (menus / pause)
Move	W A S D	Left stick (analog) / D-pad	Choose: left stick / D-pad
Shoot	Arrow keys	Right stick / A B X Y	—
Bomb	E / Shift	LB / left trigger	—
Active item	Space	RB / right trigger	—
Card / pill	Q	Right stick click	—
Pause	P / Esc	Start / Back / left stick click	Start / Back (resume)
Confirm / back	Mouse	—	A / B
Fullscreen	F11 / Alt+Enter	—	—
Screenshot	F12	—	—
Performance overlay	F3	—	—

In menus, the selected option is highlighted in pink; the D-pad or left stick chooses another, the controller presses it with A (✕ on PlayStation controllers) and goes back with B (◯), which also closes the pause screen.

Rebinding: Options → Controls → Rebind controls (from the main menu or the pause screen) changes the controls of the device you are playing with. Pick an action and press the new key or button; Reset to defaults restores the original layout. With a controller you can also choose which stick moves.

📱 Android

The same native recomp, packaged as an APK. It runs the game on the 960×720 stage used on Switch, rendered with OpenGL ES 3.0 and scaled to fill the screen.

You need:

• A 64-bit ARM phone or tablet (practically every device since 2017) with Android 7.0 or newer and OpenGL ES 3.0.
• Your Isaac.exe from your Steam copy of the game (see step 1 of the PC installation).

Installation:

1. Download IsaacRecomp.apk from Releases and install it. Android will ask you to allow "install unknown apps" for your browser or file manager.
2. Create a folder called IsaacRecomp at the root of the internal storage (next to Download, DCIM…) and copy Isaac.exe into it. Several versions work as on PC (different names, a menu to choose).
3. Open Isaac Recomp. The first time, it asks for All files access (Android 11 and newer) or for access to your files: the game, isaac.ini, the saves and log.txt all live in that folder.

Touch controls:

Action	Touch
Move	Finger on the left half: a joystick appears where it lands (analog)
Shoot	Finger on the right half: a second joystick
Bomb	Tap the bomb counter
Active item	Tap the "SPACE" box
Card / pill	Tap it (top right, when you have one)
Pause	The button next to -LIFE-, or the back button / gesture
Menus	Tap the options; on screens without options (cutscenes, title cards) a tap continues

The joysticks are semi-transparent, stay where your finger first landed and disappear when you lift it. Which side moves, the joystick size and its type (fixed base, or a base that follows the finger) can be changed in Options → Controls → Rebind controls. Bluetooth and USB controllers work exactly as on PC, and can be mixed with touch at any time.

Performance: the program renders at 720 lines and, if the device can't keep 60 fps during play, steps down to 600, 540 or 480 by itself (remembered in isaac.ini). It runs at the screen's refresh rate (90 or 120 Hz screens included), with the logic and rendering pinned to the fastest CPU cores, and audio mixed at the device's own rate through Android's low-latency audio path. To choose the resolution yourself, set render_height in isaac.ini.

🎮 Nintendo Switch (homebrew)

The same native recomp, built as a homebrew application (.nro, version 1.4.0). It contains no code or assets from Nintendo or from the game: you provide the game's Isaac.exe yourself, exactly as on PC.

You need:

• A Switch that can run homebrew, with the Homebrew Menu.
• Your Isaac.exe from your Steam copy of the game (see step 1 of the PC installation).

Installation:

1. Download IsaacRecomp_Switch.zip from Releases and copy its switch folder to the root of your SD card. You should end up with sd:/switch/isaac/isaac.nro.
2. Copy Isaac.exe into that same folder: sd:/switch/isaac/Isaac.exe. For several versions, use different names (for example Isaac-Original.exe, Isaac-WotL.exe, Isaac-Eternal.exe).
3. Open the Homebrew Menu in application mode: hold R while launching any installed game. Then pick The Binding of Isaac.

Performance: 720p in handheld mode and 1080p when docked, at 60 fps with interpolation. The game logic runs on its own CPU core, and new graphics are prepared in the background on another core.

Switch controls:

Action	Button
Move	Left stick (analog) / D-pad
Shoot	Right stick, or A / B / X / Y (→ ↓ ↑ ←)
Bomb	L
Active item	ZL
Card / pill	R
Restart the current run	Hold ZR for 5 seconds
Pause	+ or −
Menus	Stick / D-pad choose (in red), A to accept, B to go back
Performance overlay	L3 + R3

Buttons can be changed in Options → Controls → Rebind controls.

Touch screen (handheld mode): the same touch controls as on Android: joysticks on the left and right halves of the screen, taps on the bomb counter, active item and card/pill, a pause button next to -LIFE-, and taps in menus. The pause button is only shown in handheld mode.

⚙️ Configuration

isaac.ini is created on first launch next to the program (Android: in the IsaacRecomp folder; Switch: sd:/switch/isaac/isaac.ini).

Option	Default	What it does
swf	(empty)	Path to Isaac.exe, if it isn't next to the program
game	(empty)	Last chosen version: og, wotl or eternal
fullscreen	1	Borderless fullscreen (PC)
vsync	1	Vertical sync
smooth	1	Interpolation to the display refresh rate (0 = original 30 fps)
filters	1	Blur effects in cutscenes
volume	100	Master volume (0-100)
cache_mb	depends	Video memory for already rasterized graphics
low_latency	1	Keep reading input while waiting for the display (less input lag)
interp_lead	0	Experimental, up to 0.5: draw slightly ahead for less visual delay (small overshoot when stopping)
gc_after_tick	1	Free memory after each game tick has been sent to the screen, so it doesn't delay the image (0 = inside the tick, as in 1.3)
max_margin	0 (Switch: 6)	Cap, in ms, of how far behind the game the image is shown (0 = automatic, 4-30 ms). A cap keeps input delay constant in busy rooms
performance	0	1 = performance overlay always on, written to performance.txt
joystick_acceleration	1	Analog movement: speed follows how far the stick is pushed (full speed at ¾ of its travel). 0 = always full speed
touch_controls	1	Android / Switch: 0 turns off the touch joysticks, HUD taps and pause button
render_height	0	Android: rendering resolution (0 = automatic; 1080, 720, 600, 540, 480)
bind_keyboard, bind_controller, controller_move_stick, touch_move_side, touch_joystick_size, touch_joystick_type	(empty)	Written by the rebinding screen; empty = original controls

Save files:

Platform	Folder
Windows	The saves folder next to IsaacRecomp.exe
Linux	The saves folder next to isaac
Android	IsaacRecomp/saves/ in the internal storage (up to 1.3.1: IsaacRecomp/, copied over by 1.4.0)
Switch	sd:/switch/isaac/saves/ (up to 1.3.1: sd:/switch/isaac/, copied over by 1.4.0)

There is one save file per version (isaac_og_save.sol, isaac_save.sol, isaac_eternal_save.sol), and the format is the same everywhere, so you can copy saves between PC, Android and Switch. Up to 1.3.0 the PC versions saved in %APPDATA%\IsaacRecomp\WrathOfTheLamb\ (Windows) or `~/.local/share/IsaacRecomp/WrathOfTheL