Puzzle games like Lumines or Exit can be compressed to under 20 MB. Action games rarely go below 45 MB.
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In the last 12 months, groups like PSP Shrink Team and RetroMash have re-compressed old games using better algorithms, fixing bugs in previous 50 MB releases. So, "new" means "newly repacked to work better on PPSSPP v1.16+." The PSP is a discontinued platform, but downloading commercial games you do not own is copyright infringement in most countries. 50 mb highly compressed ppsspp games new