Caltrop Core is used for a lot of solo games but also plenty of larger games. Again, tactics functionality is limited, but easier to patch in. https://titanomachyrpg.itch.io/caltropcore
I don't think I'd call it tactical, but I do know that the 24XX SRD is made for microgames like that (and includes design templates as a bonus) https://jasontocci.itch.io/24xx
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https://keeper.farirpgs.com/resources/bastionland-press/mark-of-the-odd/system-reference-document/
Caltrop Core is used for a lot of solo games but also plenty of larger games. Again, tactics functionality is limited, but easier to patch in.
https://titanomachyrpg.itch.io/caltropcore
You could make it tactical pretty easily.
https://jasontocci.itch.io/24xx