feat: Simplification of UI and icons creation

tests/systems.test.js

@@ -396,7 +396,7 @@ test('events: an opportunity appears, can be claimed once, and its buff expires'
   const d = derive(s, ctx);
   stepEvents(s, ctx, 1, d, constant(0), false, totals); // first weighted type: surge
   assert.equal(s.events.current.type, 'surge');
-  assert.ok(totals.notices.some((n) => n.kind === 'event_opportunity'));
+  assert.equal(totals.notices.length, 0, 'an opportunity is shown on its card and tab, not as a pop-up');
 
   const demandBefore = derive(s, ctx).demandMultiplier;
   assert.ok(claimEvent(s, ctx, derive(s, ctx)));