:root {
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --blue-grad: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);
    --red-grad: linear-gradient(135deg, #ef4444 0%, #f43f5e 100%);
    --text-main: #1e293b;
    --text-sub: #64748b;
    --shadow: 0 20px 40px rgba(0,0,0,0.06);
    --accent: #6366f1;
}

body { font-family: 'Poppins', sans-serif; background-color: var(--bg); color: var(--text-main); display: flex; justify-content: center; align-items: center; min-height: 100vh; margin: 0; }
.app-shell { width: 380px; height: 680px; background: var(--card-bg); border-radius: 40px; box-shadow: var(--shadow); overflow: hidden; display: flex; flex-direction: column; }

/* Navigation Tabs */
.tab-nav { display: flex; padding: 20px 25px; gap: 12px; background: #fff; border-bottom: 1px solid #f1f5f9; }
.tab-btn { flex: 1; padding: 12px; border: none; background: #f1f5f9; border-radius: 14px; color: var(--text-sub); font-weight: 600; font-size: 0.75rem; cursor: pointer; transition: all 0.2s; }
.tab-btn.active { background: var(--text-main); color: white; box-shadow: 0 4px 12px rgba(0,0,0,0.1); }

.content-area { padding: 0 25px 25px; flex-grow: 1; display: none; flex-direction: column; overflow-y: auto; }
.content-area.active { display: flex; }

/* Timer Core */
.timer-circle { width: 220px; height: 220px; border-radius: 50%; display: flex; flex-direction: column; justify-content: center; align-items: center; background: white; box-shadow: 15px 15px 35px rgba(0,0,0,0.03); border: 8px solid #f8fafc; margin: 40px auto 0; position: relative; }
.timer-val { font-size: 3.5rem; font-weight: 800; -webkit-background-clip: text; -webkit-text-fill-color: transparent; transition: all 0.3s ease; }
.timer-blue { background-image: var(--blue-grad); }
.timer-red { background-image: var(--red-grad); }

/* Task & Setup UI Elements */
.todo-input-group { background: #f1f5f9; border-radius: 20px; display: flex; align-items: center; padding: 6px 6px 6px 18px; margin-bottom: 20px; }
.todo-input-group input { border: none; background: transparent; outline: none; flex: 1; font-family: inherit; font-size: 0.9rem; }
.task-item { background: white; padding: 14px; border-radius: 16px; margin-bottom: 10px; display: flex; align-items: center; gap: 12px; border: 1px solid #f1f5f9; cursor: pointer; }
.task-item.done span { color: #cbd5e1; text-decoration: line-through; }

.setup-group { margin-bottom: 20px; }
.setup-group-title { font-size: 0.7rem; text-transform: uppercase; font-weight: 800; color: #a1a1aa; border-bottom: 1px solid #f1f5f9; padding-bottom: 8px; margin-bottom: 12px; letter-spacing: 1px; }
.config-row { margin-bottom: 10px; }
.config-row label { display: block; font-size: 0.8rem; font-weight: 600; color: var(--text-sub); margin-bottom: 4px; }
.config-row input, .config-row select { width: 100%; padding: 10px; border-radius: 10px; border: 1px solid #e2e8f0; background: #f8fafc; font-family: inherit; box-sizing: border-box; }
.check-row { display: flex; align-items: center; gap: 12px; padding: 8px 0; cursor: pointer; font-size: 0.85rem; font-weight: 500; }
.check-row input { width: 18px; height: 18px; accent-color: var(--accent); }

/* Action Buttons */
.btn-play { padding: 18px; border-radius: 20px; border: none; background: var(--blue-grad); color: white; font-weight: 600; cursor: pointer; margin-top: 20px; }
.btn-restart { background: none; border: none; color: #ef4444; font-weight: 600; cursor: pointer; margin-top: 15px; font-size: 0.75rem; }

.btn-reset-settings { width: 100%; padding: 12px; background: #fee2e2; color: #ef4444; border: 2px dashed #fca5a5; border-radius: 14px; font-weight: 700; font-size: 0.75rem; cursor: pointer; margin-top: 10px; transition: all 0.2s; }
.btn-reset-settings:hover { background: #fecaca; }

/* Animations */
.beeping { animation: pulseRed 0.5s infinite; }
@keyframes pulseRed { 50% { opacity: 0.5; } }