Table of Content:

Technology, Performance and Optimization
Play Games and Save Functions
Cheats and Modification
Known Issues
Development Plan

Technology, Performance and Optimization

DOS games are using our highly optimized JSDOS library

We made huge improvement on JSDOS library:
Compared with the original JSDOS library that only outputs in mono, we support stereo output in sampling rate of 44100. Also solved audio popping and crackling, and reduced audio delay significantly.
Roland MT-32 and General MIDI are fully supported. For General MIDI you can select from soundfonts with different qualities. By default, games are set to use General MIDI first then MT-32 if both are supported.
The FPU part has been rewritten, games with special instructions are now working perfectly.
Screen lag has been reduced by more than 50%, allowing games that were originally poor experience can run normally.
We fixed bugs that caused the mouse pointer to move incorrectly in some games.
A lot of code optimization work has been done, making some games perform about 5%-10% better than the original library.
Added disc switching function and compressed CD audio support, reduces the image size while maintain the original game experience.

Even with above optimizations, running DOS games in the browser still requires a CPU with strong single-core perfomance.
(During the CPU technology high speed development in the 90s, the performance of CPU improved rapidly. For example, the game in 1994 and the game in 1996 had very different CPU requirements. So your current processor may not run all games smoothly.)
According to our estimates, the CPU 5 years ago is equivalent to 486 DX66 level, and the CPU 2 years ago is equivalent to Pentium 100 level. We expect CPUs that will be released this year to run all games smoothly under SVGA resolution.
If a game cannot run smoothly, please lower the resolution in the game settings.

Play Games and Save Functions

After downloading the game file and completing the decompression, the game will start. If it is a CD version, additional CD image downloading and decompressing will be applied.
After the game starts, the function menu will appear above the game window.
For multi-CD games, you can select the specified CD in the menu after the game prompts you to change the disk. After selecting, the download and decompression process will be performed.
CD image will be cached, so there is no need to download and decompress it the next time you open it. But once other CD version games are played, the old game cache is cleared.
For games with CD audio tracks, we provide a free CD player in C:\CDPLAYER, run playcd.bat to play CD tracks.
The Save function inside the game does not save the game progress in the browser, so you need to manually hit save button in the function menu. If you directly close the browser without saving, the progress will be lost.
There is currently no cloud save function provided, save files can be downloaded and saved locally. Local saves can also be uploaded to the browser. Note that the emulator will restart after uploading.
Save file is in standard ZIP format.

Cheats and Modification

There are two ways to modify the game or cheat:
The first is to download the save file and upload it after modification.
Second, we have prepared FPE(Fix people expert) and Kingsoft Ranger(Tools in Chinese) for each game, which can be found in C:\DDYX\FPE and C:\DDYX\gk97 after exiting the game. Those are two Cheat Engine like tools but working in DOS.
Execute C:\DDYX\FPE\FPE.BAT to start FPE, and the default wake-up key is F12.
Execute C:\DDYX\gk97\gk97.exe to start Kingsoft Ranger, the default wake-up key is double-click the left Shift key.
For specific usage, please find relevant documents by yourself.

Known Issues

Touch screen support is still limited, and is being gradually improved.
Full screen mode on mobile device does not work properly.

Development Plan

Our follow-up development plans are listed below in order of priority:
Better mobile device support.
Add more games.