I read this over. A couple things jump out. It's unclear to me if the defending creature rolls a defense against spell attacks like they do with weapon attacks. I assume you do, since it says you have to roll higher than the enemy, but it doesn't explicitly state what you're rolling against. I know it may feel redundant, but if someone is quickly checking the spell attack rules and not reading the whole page, it's unclear.
The smaller nitpick is the use of the phrase "attack of opportunity." Unless there are plans to define this elsewhere, this phrase I think is one that requires ttrpg knowledge to understand. Since the game is designed for people new to ttrpg and looking for something less taxing on rules, assuming this knowledge isn't the best.
Other than that, every thing else looks good. I like the combat crit failure and success parry and counter attack mechanic and the idea that all characters can learn anything they want.
Looking forward to more of this. I have friends who I think a rules lite game system could really benefit..