Tide Pool Game

I've been working on an educational game to teach people about the keystone species hypothesis in ecology. It uses sea stars in a tide pool based on Robert Paine's original work on the subject. I want to make an interesting game that reinforces the theory. My plan is to release it as a PnP game so that teachers can use it in a classroom.

The basic idea is that each player (from 2-5) controls a sea star. The tide pool is a 5x5 grid of cards. Each card has a color (associated with a sea star) and a point value. Some cards have no points and represent empty space. A player turn consists of moving and "eating" one card, replacing it from the deck. If the color of the card matches the sea star, the player gets full points, otherwise they get one point.

After a set number of turns (maybe 10), the tide rolls in. Players write down their point total and reshuffle the deck. When the tide rolls out, they start again, but now there is a sun star in the middle. Sun stars eat other sea stars so now the players will have to avoid the predator while they try to eat the most points. The sun star will move randomly at the end of each round (probably by a d8) and if it lands on a player they will get eaten and discard all of their cards. If it lands next to them it grabs them and they have to detach an arm (discard a random card) to escape.

Most total points after both rounds is the winner.

Players will find that they have fewer points, but there is less empty space with the Sun star present. That is the ecology lesson. When a keystone species (like the sun star) is present - even in very small numbers - it alters the behavior and balance of an ecosystem.

Some places where I could use some suggestions:
Point values of cards: I've tested it with 1-3 points and it works well. I want to simulate the idea of a preferred food (each color will be a different tide pool species), and the fact that sea stars are generalists (they will eat many different things). The problem with 1 point cards is that the color doesn't matter. Mismatched colors all count as 1 point. Should I make them 2-4, or does that even matter?

Movement:
I've been testing with movement in any of the 8 directions. Players can either move twice, move then eat, or just eat (no eat then move). Does that make sense?

Sun star:
Currently it moves twice in a turn according to a d8. I have a little compass on the image to indicate directions. This often leaves it moving back and forth, but that seems okay to me. How should I handle it hitting an edge or corner? Re-rolling seems obvious, but when it hits a corner there will be a lot of re-rolls (5/8 of the time).

Thanks for reading! I appreciate any and all comments you may have for me.